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Discourses by Thomas H. Huxley

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The contents of the present volume, with three exceptions, are either
popular lectures, or addresses delivered to scientific bodies with which
I have been officially connected. I am not sure which gave me the more
trouble. For I have not been one of those fortunate persons who are able
to regard a popular lecture as a mere _hors d'oeuvre_, unworthy of being
ranked among the serious efforts of a philosopher; and who keep their
fame as scientific hierophants unsullied by attempts--at least of the
successful sort--to be understanded of the people.

On the contrary, I found that the task of putting the truths learned in
the field, the laboratory and the museum, into language which, without
bating a jot of scientific accuracy shall be generally intelligible,
taxed such scientific and literary faculty as I possessed to the
uttermost; indeed my experience has furnished me with no better
corrective of the tendency to scholastic pedantry which besets all those
who are absorbed in pursuits remote from the common ways of men, and
become habituated to think and speak in the technical dialect of their
own little world, as if there were no other.

If the popular lecture thus, as I believe, finds one moiety of its
justification in the self-discipline of the lecturer, it surely finds the
other half in its effect on the auditory. For though various sadly
comical experiences of the results of my own efforts have led me to
entertain a very moderate estimate of the purely intellectual value of
lectures; though I venture to doubt if more than one in ten of an average
audience carries away an accurate notion of what the speaker has been
driving at; yet is that not equally true of the oratory of the hustings,
of the House of Commons, and even of the pulpit?

Yet the children of this world are wise in their generation; and both the
politician and the priest are justified by results. The living voice has
an influence over human action altogether independent of the intellectual
worth of that which it utters. Many years ago, I was a guest at a great
City dinner. A famous orator, endowed with a voice of rare flexibility
and power; a born actor, ranging with ease through every part, from
refined comedy to tragic unction, was called upon to reply to a toast.
The orator was a very busy man, a charming conversationalist and by no
means despised a good dinner; and, I imagine, rose without having given a
thought to what he was going to say. The rhythmic roll of sound was
admirable, the gestures perfect, the earnestness impressive; nothing was
lacking save sense and, occasionally, grammar. When the speaker sat down
the applause was terrific and one of my neighbours was especially
enthusiastic. So when he had quieted down, I asked him what the orator
had said. And he could not tell me.

That sagacious person John Wesley, is reported to have replied to some
one who questioned the propriety of his adaptation of sacred words to
extremely secular airs, that he did not see why the Devil should be left
in possession of all the best tunes. And I do not see why science should
not turn to account the peculiarities of human nature thus exploited by
other agencies: all the more because science, by the nature of its being,
cannot desire to stir the passions, or profit by the weaknesses, of human
nature. The most zealous of popular lecturers can aim at nothing more
than the awakening of a sympathy for abstract truth, in those who do not
really follow his arguments; and of a desire to know more and better in
the few who do.

At the same time it must be admitted that the popularization of science,
whether by lecture or essay, has its drawbacks. Success in this
department has its perils for those who succeed. The "people who fail"
take their revenge, as we have recently had occasion to observe, by
ignoring all the rest of a man's work and glibly labelling him a more
popularizer. If the falsehood were not too glaring, they would say the
same of Faraday and Helmholtz and Kelvin.

On the other hand, of the affliction caused by persons who think that
what they have picked up from popular exposition qualifies them for
discussing the great problems of science, it may be said, as the Radical
toast said of the power of the Crown in bygone days, that it "has
increased, is increasing, and ought to be diminished." The oddities of
"English as she is spoke" might be abundantly paralleled by those of
"Science as she is misunderstood" in the sermon, the novel, and the
leading article; and a collection of the grotesque travesties of
scientific conceptions, in the shape of essays on such trifles as "the
Nature of Life" and the "Origin of All Things," which reach me, from time
to time, might well be bound up with them.

The tenth essay in this volume unfortunately brought me, I will not say
into collision, but into a position of critical remonstrance with regard
to some charges of physical heterodoxy, brought by my distinguished
friend Lord Kelvin, against British Geology. As President of the
Geological Society of London at that time (1869), I thought I might
venture to plead that we were not such heretics as we seemed to be; and
that, even if we were, recantation would not affect the question of

I am glad to see that Lord Kelvin has just reprinted his reply to my
plea,[1] and I refer the reader to it. I shall not presume to question
anything, that on such ripe consideration, Lord Kelvin has to say upon
the physical problems involved. But I may remark that no one can have
asserted more strongly than I have done, the necessity of looking to
physics and mathematics, for help in regard to the earliest history of
the globe. (See pp. 108 and 109 of this volume.)

[Footnote 1: _Popular Lectures and Addresses._ II. Macmillan and Co.

And I take the opportunity of repeating the opinion, that, whether what
we call geological time has the lower limit assigned to it by Lord
Kelvin, or the higher assumed by other philosophers; whether the germs of
all living things have originated in the globe itself, or whether they
have been imported on, or in, meteorites from without, the problem of the
origin of those successive Faunae and Florae of the earth, the existence of
which is fully demonstrated by paleontology remains exactly where it was.

For I think it will be admitted, that the germs brought to us by
meteorites, if any, were not ova of elephants, nor of crocodiles; not
cocoa-nuts nor acorns; not even eggs of shell-fish and corals; but only
those of the lowest forms of animal and vegetable life. Therefore, since
it is proved that, from a very remote epoch of geological time, the earth
has been peopled by a continual succession of the higher forms of animals
and plants, these either must have been created, or they have arisen by
evolution. And in respect of certain groups of animals, the well-
established facts of paleontology leave no rational doubt that they arose
by the latter method.

In the second place, there are no data whatever, which justify the
biologist in assigning any, even approximately definite, period of time,
either long or short, to the evolution of one species from another by the
process of variation and selection. In the ninth of the following essays,
I have taken pains to prove that the change of animals has gone on at
very different rates in different groups of living beings; that some
types have persisted with little change from the paleozoic epoch till
now, while others have changed rapidly within the limits of an epoch. In
1862 (see below p. 303, 304) in 1863 (vol. II., p. 461) and again in 1864
(ibid., p. 89-91) I argued, not as a matter of speculation, but, from
paleontological facts, the bearing of which I believe, up to that time,
had not been shown, that any adequate hypothesis of the causes of
evolution must be consistent with progression, stationariness and
retrogression, of the same type at different epochs; of different types
in the same epoch; and that Darwin's hypothesis fulfilled these

According to that hypothesis, two factors are at work, variation and
selection. Next to nothing is known of the causes of the former process;
nothing whatever of the time required for the production of a certain
amount of deviation from the existing type. And, as respects selection,
which operates by extinguishing all but a small minority of variations,
we have not the slightest means of estimating the rapidity with which it
does its work. All that we are justified in saying is that the rate at
which it takes place may vary almost indefinitely. If the famous paint-
root of Florida, which kills white pigs but not black ones, were abundant
and certain in its action, black pigs might be substituted for white in
the course of two or three years. If, on the other hand, it was rare and
uncertain in action, the white pigs might linger on for centuries.



_April, 1894._



(A Lecture delivered to the working men of Norwich during the meeting of
the British Association.)






YEAST [1871]


(A Lecture delivered at the Philosophical Institute, Bradford.)


(A Friday evening Lecture delivered at the Royal Institution.)


(A Lecture delivered at the South Kensington Museum.)


(The Presidential Address to the Meeting of the British Association for
the Advancement of Science at Liverpool.)


(Address to the Geological Society on behalf of the President by one of
the Secretaries.)


(Presidential Address to the Geological Society.)


(Presidential Address to the Geological Society.)




If a well were sunk at our feet in the midst of the city of Norwich, the
diggers would very soon find themselves at work in that white substance
almost too soft to be called rock, with which we are all familiar as

Not only here, but over the whole county of Norfolk, the well-sinker
might carry his shaft down many hundred feet without coming to the end of
the chalk; and, on the sea-coast, where the waves have pared away the
face of the land which breasts them, the scarped faces of the high cliffs
are often wholly formed of the same material. Northward, the chalk may be
followed as far as Yorkshire; on the south coast it appears abruptly in
the picturesque western bays of Dorset, and breaks into the Needles of
the Isle of Wight; while on the shores of Kent it supplies that long line
of white cliffs to which England owes her name of Albion.

Were the thin soil which covers it all washed away, a curved band of
white chalk, here broader, and there narrower, might be followed
diagonally across England from Lulworth in Dorset, to Flamborough Head in
Yorkshire--a distance of over 280 miles as the crow flies. From this band
to the North Sea, on the east, and the Channel, on the south, the chalk
is largely hidden by other deposits; but, except in the Weald of Kent and
Sussex, it enters into the very foundation of all the south-eastern

Attaining, as it does in some places, a thickness of more than a thousand
feet, the English chalk must be admitted to be a mass of considerable
magnitude. Nevertheless, it covers but an insignificant portion of the
whole area occupied by the chalk formation of the globe, much of which
has the same general characters as ours, and is found in detached
patches, some less, and others more extensive, than the English. Chalk
occurs in north-west Ireland; it stretches over a large part of France,--
the chalk which underlies Paris being, in fact, a continuation of that of
the London basin; it runs through Denmark and Central Europe, and extends
southward to North Africa; while eastward, it appears in the Crimea and
in Syria, and may be traced as far as the shores of the Sea of Aral, in
Central Asia. If all the points at which true chalk occurs were
circumscribed, they would lie within an irregular oval about 3,000 miles
in long diameter--the area of which would be as great as that of Europe,
and would many times exceed that of the largest existing inland sea--the

Thus the chalk is no unimportant element in the masonry of the earth's
crust, and it impresses a peculiar stamp, varying with the conditions to
which it is exposed, on the scenery of the districts in which it occurs.
The undulating downs and rounded coombs, covered with sweet-grassed turf,
of our inland chalk country, have a peacefully domestic and mutton-
suggesting prettiness, but can hardly be called either grand or
beautiful. But on our southern coasts, the wall-sided cliffs, many
hundred feet high, with vast needles and pinnacles standing out in the
sea, sharp and solitary enough to serve as perches for the wary
cormorant, confer a wonderful beauty and grandeur upon the chalk
headlands. And, in the East, chalk has its share in the formation of some
of the most venerable of mountain ranges, such as the Lebanon.

What is this wide-spread component of the surface of the earth? and
whence did it come?

You may think this no very hopeful inquiry. You may not unnaturally
suppose that the attempt to solve such problems as these can lead to no
result, save that of entangling the inquirer in vague speculations,
incapable of refutation and of verification. If such were really the
case, I should have selected some other subject than a "piece of chalk"
for my discourse. But, in truth, after much deliberation, I have been
unable to think of any topic which would so well enable me to lead you to
see how solid is the foundation upon which some of the most startling
conclusions of physical science rest.

A great chapter of the history of the world is written in the chalk. Few
passages in the history of man can be supported by such an overwhelming
mass of direct and indirect evidence as that which testifies to the truth
of the fragment of the history of the globe, which I hope to enable you
to read, with your own eyes, to-night. Let me add, that few chapters of
human history have a more profound significance for ourselves. I weigh my
words well when I assert, that the man who should know the true history
of the bit of chalk which every carpenter carries about in his breeches-
pocket, though ignorant of all other history, is likely, if he will think
his knowledge out to its ultimate results, to have a truer, and therefore
a better, conception of this wonderful universe, and of man's relation to
it, than the most learned student who is deep-read in the records of
humanity and ignorant of those of Nature.

The language of the chalk is not hard to learn, not nearly so hard as
Latin, if you only want to get at the broad features of the story it has
to tell; and I propose that we now set to work to spell that story out

We all know that if we "burn" chalk the result is quicklime. Chalk, in
fact, is a compound of carbonic acid gas, and lime, and when you make it
very hot the carbonic acid flies away and the lime is left. By this
method of procedure we see the lime, but we do not see the carbonic acid.
If, on the other hand, you were to powder a little chalk and drop it into
a good deal of strong vinegar, there would be a great bubbling and
fizzing, and, finally, a clear liquid, in which no sign of chalk would
appear. Here you see the carbonic acid in the bubbles; the lime,
dissolved in the vinegar, vanishes from sight. There are a great many
other ways of showing that chalk is essentially nothing but carbonic acid
and quicklime. Chemists enunciate the result of all the experiments which
prove this, by stating that chalk is almost wholly composed of "carbonate
of lime."

It is desirable for us to start from the knowledge of this fact, though
it may not seem to help us very far towards what we seek. For carbonate
of lime is a widely-spread substance, and is met with under very various
conditions. All sorts of limestones are composed of more or less pure
carbonate of lime. The crust which is often deposited by waters which
have drained through limestone rocks, in the form of what are called
stalagmites and stalactites, is carbonate of lime. Or, to take a more
familiar example, the fur on the inside of a tea-kettle is carbonate of
lime; and, for anything chemistry tells us to the contrary, the chalk
might be a kind of gigantic fur upon the bottom of the earth-kettle,
which is kept pretty hot below.

Let us try another method of making the chalk tell us its own history. To
the unassisted eye chalk looks simply like a very loose and open kind of
stone. But it is possible to grind a slice of chalk down so thin that you
can see through it--until it is thin enough, in fact, to be examined with
any magnifying power that may be thought desirable. A thin slice of the
fur of a kettle might be made in the same way. If it were examined
microscopically, it would show itself to be a more or less distinctly
laminated mineral substance, and nothing more.

But the slice of chalk presents a totally different appearance when
placed under the microscope. The general mass of it is made up of very
minute granules; but, imbedded in this matrix, are innumerable bodies,
some smaller and some larger, but, on a rough average, not more than a
hundredth of an inch in diameter, having a well-defined shape and
structure. A cubic inch of some specimens of chalk may contain hundreds
of thousands of these bodies, compacted together with incalculable
millions of the granules.

The examination of a transparent slice gives a good notion of the manner
in which the components of the chalk are arranged, and of their relative
proportions. But, by rubbing up some chalk with a brush in water and then
pouring off the milky fluid, so as to obtain sediments of different
degrees of fineness, the granules and the minute rounded bodies may be
pretty well separated from one another, and submitted to microscopic
examination, either as opaque or as transparent objects. By combining the
views obtained in these various methods, each of the rounded bodies may
be proved to be a beautifully-constructed calcareous fabric, made up of a
number of chambers, communicating freely with one another. The chambered
bodies are of various forms. One of the commonest is something like a
badly-grown raspberry, being formed of a number of nearly globular
chambers of different sizes congregated together. It is called
_Globigerina_, and some specimens of chalk consist of little else than
_Globigerinoe_ and granules. Let us fix our attention upon the
_Globigerina_. It is the spoor of the game we are tracking. If we can
learn what it is and what are the conditions of its existence, we shall
see our way to the origin and past history of the chalk.

A suggestion which may naturally enough present itself is, that these
curious bodies are the result of some process of aggregation which has
taken place in the carbonate of lime; that, just as in winter, the rime
on our windows simulates the most delicate and elegantly arborescent
foliage--proving that the mere mineral water may, under certain
conditions, assume the outward form of organic bodies--so this mineral
substance, carbonate of lime, hidden away in the bowels of the earth, has
taken the shape of these chambered bodies. I am not raising a merely
fanciful and unreal objection. Very learned men, in former days, have
even entertained the notion that all the formed things found in rocks are
of this nature; and if no such conception is at present held to be
admissible, it is because long and varied experience has now shown that
mineral matter never does assume the form and structure we find in
fossils. If any one were to try to persuade you that an oyster-shell
(which is also chiefly composed of carbonate of lime) had crystallized
out of sea-water, I suppose you would laugh at the absurdity. Your
laughter would be justified by the fact that all experience tends to show
that oyster-shells are formed by the agency of oysters, and in no other
way. And if there were no better reasons, we should be justified, on like
grounds, in believing that _Globigerina_ is not the product of anything
but vital activity.

Happily, however, better evidence in proof of the organic nature of the
_Globigerinoe_ than that of analogy is forthcoming. It so happens that
calcareous skeletons, exactly similar to the _Globigerinoe_ of the chalk,
are being formed, at the present moment, by minute living creatures,
which flourish in multitudes, literally more numerous than the sands of
the sea-shore, over a large extent of that part of the earth's surface
which is covered by the ocean.

The history of the discovery of these living _Globigerinoe_, and of the
part which they play in rock building, is singular enough. It is a
discovery which, like others of no less scientific importance, has
arisen, incidentally, out of work devoted to very different and
exceedingly practical interests. When men first took to the sea, they
speedily learned to look out for shoals and rocks; and the more the
burthen of their ships increased, the more imperatively necessary it
became for sailors to ascertain with precision the depth of the waters
they traversed. Out of this necessity grew the use of the lead and
sounding line; and, ultimately, marine-surveying, which is the recording
of the form of coasts and of the depth of the sea, as ascertained by the
sounding-lead, upon charts.

At the same time, it became desirable to ascertain and to indicate the
nature of the sea-bottom, since this circumstance greatly affects its
goodness as holding ground for anchors. Some ingenious tar, whose name
deserves a better fate than the oblivion into which it has fallen,
attained this object by "arming" the bottom of the lead with a lump of
grease, to which more or less of the sand or mud, or broken shells, as
the case might be, adhered, and was brought to the surface. But, however
well adapted such an apparatus might be for rough nautical purposes,
scientific accuracy could not be expected from the armed lead, and to
remedy its defects (especially when applied to sounding in great depths)
Lieut. Brooke, of the American Navy, some years ago invented a most
ingenious machine, by which a considerable portion of the superficial
layer of the sea-bottom can be scooped out and brought up from any depth
to which the lead descends. In 1853, Lieut. Brooke obtained mud from the
bottom of the North Atlantic, between Newfoundland and the Azores, at a
depth of more than 10,000 feet, or two miles, by the help of this
sounding apparatus. The specimens were sent for examination to Ehrenberg
of Berlin, and to Bailey of West Point, and those able microscopists
found that this deep-sea mud was almost entirely composed of the
skeletons of living organisms--the greater proportion of these being just
like the _Globigerinoe_ already known to occur in the chalk.

Thus far, the work had been carried on simply in the interests of
science, but Lieut. Brooke's method of sounding acquired a high
commercial value, when the enterprise of laying down the telegraph-cable
between this country and the United States was undertaken. For it became
a matter of immense importance to know, not only the depth of the sea
over the whole line along which the cable was to be laid, but the exact
nature of the bottom, so as to guard against chances of cutting or
fraying the strands of that costly rope. The Admiralty consequently
ordered Captain Dayman, an old friend and shipmate of mine, to ascertain
the depth over the whole line of the cable, and to bring back specimens
of the bottom. In former days, such a command as this might have sounded
very much like one of the impossible things which the young Prince in the
Fairy Tales is ordered to do before he can obtain the hand of the
Princess. However, in the months of June and July, 1857, my friend
performed the task assigned to him with great expedition and precision,
without, so far as I know, having met with any reward of that kind. The
specimens or Atlantic mud which he procured were sent to me to be
examined and reported upon.[1]

[Footnote 1: See Appendix to Captain Dayman's _Deep-sea Soundings in the
North Atlantic Ocean between Ireland and Newfoundland, made in H.M.S.
"Cyclops_." Published by order of the Lords Commissioners of the
Admiralty, 1858. They have since formed the subject of an elaborate
Memoir by Messrs. Parker and Jones, published in the _Philosophical
Transactions_ for 1865.]

The result of all these operations is, that we know the contours and the
nature of the surface-soil covered by the North Atlantic for a distance
of 1,700 miles from east to west, as well as we know that of any part of
the dry land. It is a prodigious plain--one of the widest and most even
plains in the world. If the sea were drained off, you might drive a
waggon all the way from Valentia, on the west coast of Ireland, to
Trinity Bay, in Newfoundland. And, except upon one sharp incline about
200 miles from Valentia, I am not quite sure that it would even be
necessary to put the skid on, so gentle are the ascents and descents upon
that long route. From Valentia the road would lie down-hill for about 200
miles to the point at which the bottom is now covered by 1,700 fathoms of
sea-water. Then would come the central plain, more than a thousand miles
wide, the inequalities of the surface of which would be hardly
perceptible, though the depth of water upon it now varies from 10,000 to
15,000 feet; and there are places in which Mont Blanc might be sunk
without showing its peak above water. Beyond this, the ascent on the
American side commences, and gradually leads, for about 300 miles, to the
Newfoundland shore.

Almost the whole of the bottom of this central plain (which extends for
many hundred miles in a north and south direction) is covered by a fine
mud, which, when brought to the surface, dries into a greyish white
friable substance. You can write with this on a blackboard, if you are so
inclined; and, to the eye, it is quite like very soft, grayish chalk.
Examined chemically, it proves to be composed almost wholly of carbonate
of lime; and if you make a section of it, in the same way as that of the
piece of chalk was made, and view it with the microscope, it presents
innumerable _Globigerinoe_ embedded in a granular matrix. Thus this deep-
sea mud is substantially chalk. I say substantially, because there are a
good many minor differences; but as these have no bearing on the question
immediately before us,--which is the nature of the _Globigerinoe_ of the
chalk,--it is unnecessary to speak of them.

_Globigerinoe_ of every size, from the smallest to the largest, are
associated together in the Atlantic mud, and the chambers of many are
filled by a soft animal matter. This soft substance is, in fact, the
remains of the creature to which the _Globigerinoe_ shell, or rather
skeleton, owes its existence--and which is an animal of the simplest
imaginable description. It is, in fact, a mere particle of living jelly,
without defined parts of any kind--without a mouth, nerves, muscles, or
distinct organs, and only manifesting its vitality to ordinary
observation by thrusting out and retracting from all parts of its
surface, long filamentous processes, which serve for arms and legs. Yet
this amorphous particle, devoid of everything which, in the higher
animals, we call organs, is capable of feeding, growing, and multiplying;
of separating from the ocean the small proportion of carbonate of lime
which is dissolved in sea-water; and of building up that substance into a
skeleton for itself, according to a pattern which can be imitated by no
other known agency.

The notion that animals can live and flourish in the sea, at the vast
depths from which apparently living _Globigerinoe_; have been brought up,
does not agree very well with our usual conceptions respecting the
conditions of animal life; and it is not so absolutely impossible as it
might at first sight appear to be, that the _Globigcrinoe_ of the
Atlantic sea-bottom do not live and die where they are found.

As I have mentioned, the soundings from the great Atlantic plain are
almost entirely made up of _Globigerinoe_, with the granules which have
been mentioned, and some few other calcareous shells; but a small
percentage of the chalky mud--perhaps at most some five per cent. of it--
is of a different nature, and consists of shells and skeletons composed
of silex, or pure flint. These silicious bodies belong partly to the
lowly vegetable organisms which are called _Diatomaceoe_, and partly to
the minute, and extremely simple, animals, termed _Radiolaria_. It is
quite certain that these creatures do not live at the bottom of the
ocean, but at its surface--where they may be obtained in prodigious
numbers by the use of a properly constructed net. Hence it follows that
these silicious organisms, though they are not heavier than the lightest
dust, must have fallen, in some cases, through fifteen thousand feet of
water, before they reached their final resting-place on the ocean floor.
And considering how large a surface these bodies expose in proportion to
their weight, it is probable that they occupy a great length of time in
making their burial journey from the surface of the Atlantic to the

But if the _Radiolaria_ and Diatoms are thus rained upon the bottom of
the sea, from the superficial layer of its waters in which they pass
their lives, it is obviously possible that the _Globigerinoe_ may be
similarly derived; and if they were so, it would be much more easy to
understand how they obtain their supply of food than it is at present.
Nevertheless, the positive and negative evidence all points the other
way. The skeletons of the full-grown, deep-sea _Globigerinoe_ are so
remarkably solid and heavy in proportion to their surface as to seem
little fitted for floating; and, as a matter of fact, they are not to be
found along with the Diatoms and _Radiolaria_ in the uppermost stratum of
the open ocean. It has been observed, again, that the abundance of
_Globigerinoe_, in proportion to other organisms, of like kind, increases
with the depth of the sea; and that deep-water _Globigerinoe_ are larger
than those which live in shallower parts of the sea; and such facts
negative the supposition that these organisms have been swept by currents
from the shallows into the deeps of the Atlantic. It therefore seems to
be hardly doubtful that these wonderful creatures live and die at the
depths in which they are found.[2]

[Footnote 2: During the cruise of H.M.S. _Bulldog_, commanded by Sir
Leopold M'Clintock, in 1860, living star-fish were brought up, clinging
to the lowest part of the sounding-line, from a depth of 1,260 fathoms,
midway between Cape Farewell, in Greenland, and the Rockall banks. Dr.
Wallich ascertained that the sea-bottom at this point consisted of the
ordinary _Globigerina_ ooze, and that the stomachs of the star-fishes
were full of _Globigerinoe_. This discovery removes all objections to the
existence of living _Globigerinoe_ at great depths, which are based upon
the supposed difficulty of maintaining animal life under such conditions;
and it throws the burden of proof upon those who object to the
supposition that the _Globigerinoe_ live and die where they are found.]

However, the important points for us are, that the living _Globigerinoe_
are exclusively marine animals, the skeletons of which abound at the
bottom of deep seas; and that there is not a shadow of reason for
believing that the habits of the _Globigerinoe_ of the chalk differed
from those of the existing species. But if this be true, there is no
escaping the conclusion that the chalk itself is the dried mud of an
ancient deep sea.

In working over the soundings collected by Captain Dayman, I was
surprised to find that many of what I have called the "granules" of that
mud were not, as one might have been tempted to think at first, the more
powder and waste of _Globigerinoe_, but that they had a definite form and
size. I termed these bodies "_coccoliths_," and doubted their organic
nature. Dr. Wallich verified my observation, and added the interesting
discovery that, not unfrequently, bodies similar to these "coccoliths"
were aggregated together into spheroids, which lie termed
"_coccospheres_." So far as we knew, these bodies, the nature of which is
extremely puzzling and problematical, were peculiar to the Atlantic
soundings. But, a few years ago, Mr. Sorby, in making a careful
examination of the chalk by means of thin sections and otherwise,
observed, as Ehrenberg had done before him, that much of its granular
basis possesses a definite form. Comparing these formed particles with
those in the Atlantic soundings, he found the two to be identical; and
thus proved that the chalk, like the surroundings, contains these
mysterious coccoliths and coccospheres. Here was a further and most
interesting confirmation, from internal evidence, of the essential
identity of the chalk with modern deep-sea mud. _Globigerinoe_,
coccoliths, and coccospheres are found as the chief constituents of both,
and testify to the general similarity of the conditions under which both
have been formed.[3]

[Footnote 3: I have recently traced out the development of the
"coccoliths" from a diameter of 1/7000th of an inch up to their largest
size (which is about 1/1000th), and no longer doubt that they are
produced by independent organisms, which, like the _Globigerinoe_, live
and die at the bottom of the sea.]

The evidence furnished by the hewing, facing, and superposition of the
stones of the Pyramids, that these structures were built by men, has no
greater weight than the evidence that the chalk was built by
_Globigerinoe_; and the belief that those ancient pyramid-builders were
terrestrial and air-breathing creatures like ourselves, is not better
based than the conviction that the chalk-makers lived in the sea. But as
our belief in the building of the Pyramids by men is not only grounded on
the internal evidence afforded by these structures, but gathers strength
from multitudinous collateral proofs, and is clinched by the total
absence of any reason for a contrary belief; so the evidence drawn from
the _Globigerinoe_ that the chalk is an ancient sea-bottom, is fortified
by innumerable independent lines of evidence; and our belief in the truth
of the conclusion to which all positive testimony tends, receives the
like negative justification from the fact that no other hypothesis has a
shadow of foundation.

It may be worth while briefly to consider a few of these collateral
proofs that the chalk was deposited at the bottom of the sea. The great
mass of the chalk is composed, as we have seen, of the skeletons of
_Globigerinoe_, and other simple organisms, imbedded in granular matter.
Here and there, however, this hardened mud of the ancient sea reveals the
remains of higher animals which have lived and died, and left their hard
parts in the mud, just as the oysters die and leave their shells behind
them, in the mud of the present seas.

There are, at the present day, certain groups of animals which are never
found in fresh waters, being unable to live anywhere but in the sea. Such
are the corals; those corallines which are called _Polyzoa_; those
creatures which fabricate the lamp-shells, and are called _Brachiopoda_;
the pearly _Nautilus_, and all animals allied to it; and all the forms of
sea-urchins and star-fishes. Not only are all these creatures confined to
salt water at the present day; but, so far as our records of the past go,
the conditions of their existence have been the same: hence, their
occurrence in any deposit is as strong evidence as can be obtained, that
that deposit was formed in the sea. Now the remains of animals of all the
kinds which have been enumerated, occur in the chalk, in greater or less
abundance; while not one of those forms of shell-fish which are
characteristic of fresh water has yet been observed in it.

When we consider that the remains of more than three thousand distinct
species of aquatic animals have been discovered among the fossils of the
chalk, that the great majority of them are of such forms as are now met
with only in the sea, and that there is no reason to believe that any one
of them inhabited fresh water--the collateral evidence that the chalk
represents an ancient sea-bottom acquires as great force as the proof
derived from the nature of the chalk itself. I think you will now allow
that I did not overstate my case when I asserted that we have as strong
grounds for believing that all the vast area of dry land, at present
occupied by the chalk, was once at the bottom of the sea, as we have for
any matter of history whatever; while there is no justification for any
other belief.

No less certain it is that the time during which the countries we now
call south-east England, France, Germany, Poland, Russia, Egypt, Arabia,
Syria, were more or less completely covered by a deep sea, was of
considerable duration. We have already seen that the chalk is, in places,
more than a thousand feet thick. I think you will agree with me, that it
must have taken some time for the skeletons of animalcules of a hundredth
of an inch in diameter to heap up such a mass as that. I have said that
throughout the thickness of the chalk the remains of other animals are
scattered. These remains are often in the most exquisite state of
preservation. The valves of the shell-fishes are commonly adherent; the
long spines of some of the sea-urchins, which would be detached by the
smallest jar, often remain in their places. In a word, it is certain that
these animals have lived and died when the place which they now occupy
was the surface of as much of the chalk as had then been deposited; and
that each has been covered up by the layer of _Globigerina_ mud, upon
which the creatures imbedded a little higher up have, in like manner,
lived and died. But some of these remains prove the existence of reptiles
of vast size in the chalk sea. These lived their time, and had their
ancestors and descendants, which assuredly implies time, reptiles being
of slow growth.

There is more curious evidence, again, that the process of covering up,
or, in other words, the deposit of _Globigerina_ skeletons, did not go on
very fast. It is demonstrable that an animal of the cretaceous sea might
die, that its skeleton might lie uncovered upon the sea-bottom long
enough to lose all its outward coverings and appendages by putrefaction;
and that, after this had happened, another animal might attach itself to
the dead and naked skeleton, might grow to maturity, and might itself die
before the calcareous mud had buried the whole.

Cases of this kind are admirably described by Sir Charles Lyell. He
speaks of the frequency with which geologists find in the chalk a
fossilized sea-urchin, to which is attached the lower valve of a
_Crania_. This is a kind of shell-fish, with a shell composed of two
pieces, of which, as in the oyster, one is fixed and the other free.

"The upper valve is almost invariably wanting, though occasionally found
in a perfect state of preservation in the white chalk at some distance.
In this case, we see clearly that the sea-urchin first lived from youth
to age, then died and lost its spines, which were carried away. Then the
young _Crania_ adhered to the bared shell, grew and perished in its turn;
after which, the upper valve was separated from the lower, before the
Echinus became enveloped in chalky mud."[4]

A specimen in the Museum of Practical Geology, in London, still further
prolongs the period which must have elapsed between the death of the sea-
urchin, and its burial by the _Globigerinoe_. For the outward face of the
valve of a _Crania_, which is attached to a sea-urchin, (_Micraster_), is
itself overrun by an incrusting coralline, which spreads thence over more
or less of the surface of the sea-urchin. It follows that, after the
upper valve of the _Crania_ fell off, the surface of the attached valve
must have remained exposed long enough to allow of the growth of the
whole coralline, since corallines do not live embedded in mud.[4]

[Footnote 4: _Elements of Geology_, by Sir Charles Lyell, Bart. F.B.S.,
p. 23.]

The progress of knowledge may, one day, enable us to deduce from such
facts as these the maximum rate at which the chalk can have accumulated,
and thus to arrive at the minimum duration of the chalk period. Suppose
that the valve of the _Cronia_ upon which a coralline has fixed itself in
the way just described, is so attached to the sea-urchin that no part of
it is more than an inch above the face upon which the sea-urchin rests.
Then, as the coralline could not have fixed itself, if the _Crania_ had
been covered up with chalk mud, and could not have lived had itself been
so covered, it follows, that an inch of chalk mud could not have
accumulated within the time between the death and decay of the soft parts
of the sea-urchin and the growth of the coralline to the full size which
it has attained. If the decay of the soft parts of the sea-urchin; the
attachment, growth to maturity, and decay of the _Crania_; and the
subsequent attachment and growth of the coralline, took a year (which is
a low estimate enough), the accumulation of the inch of chalk must have
taken more than a year: and the deposit of a thousand feet of chalk must,
consequently, have taken more than twelve thousand years.

The foundation of all this calculation is, of course, a knowledge of the
length of time the _Crania_ and the coralline needed to attain their full
size; and, on this head, precise knowledge is at present wanting. But
there are circumstances which tend to show, that nothing like an inch of
chalk has accumulated during the life of a _Crania_; and, on any probable
estimate of the length of that life, the chalk period must have had a
much longer duration than that thus roughly assigned to it.

Thus, not only is it certain that the chalk is the mud of an ancient sea-
bottom; but it is no less certain, that the chalk sea existed during an
extremely long period, though we may not be prepared to give a precise
estimate of the length of that period in years. The relative duration is
clear, though the absolute duration may not be definable. The attempt to
affix any precise date to the period at which the chalk sea began, or
ended, its existence, is baffled by difficulties of the same kind. But
the relative age of the cretaceous epoch may be determined with as great
ease and certainty as the long duration of that epoch.

You will have heard of the interesting discoveries recently made, in
various parts of Western Europe, of flint implements, obviously worked
into shape by human hands, under circumstances which show conclusively
that man is a very ancient denizen of these regions. It has been proved
that the whole populations of Europe, whose existence has been revealed
to us in this way, consisted of savages, such as the Esquimaux are now;
that, in the country which is now France, they hunted the reindeer, and
were familiar with the ways of the mammoth and the bison. The physical
geography of France was in those days different from what it is now--the
river Somme, for instance, having cut its bed a hundred feet deeper
between that time and this; and, it is probable, that the climate was
more like that of Canada or Siberia, than that of Western Europe.

The existence of these people is forgotten even in the traditions of the
oldest historical nations. The name and fame of them had utterly vanished
until a few years back; and the amount of physical change which has been
effected since their day renders it more than probable that, venerable as
are some of the historical nations, the workers of the chipped flints of
Hoxne or of Amiens are to them, as they are to us, in point of antiquity.
But, if we assign to these hoar relics of long-vanished generations of
men the greatest age that can possibly be claimed for them, they are not
older than the drift, or boulder clay, which, in comparison with the
chalk, is but a very juvenile deposit. You need go no further than your
own sea-board for evidence of this fact. At one of the most charming
spots on the coast of Norfolk, Cromer, you will see the boulder clay
forming a vast mass, which lies upon the chalk, and must consequently
have come into existence after it. Huge boulders of chalk are, in fact,
included in the clay, and have evidently been brought to the position
they now occupy by the same agency as that which has planted blocks of
syenite from Norway side by side with them.

The chalk, then, is certainly older than the boulder clay. If you ask how
much, I will again take you no further than the same spot upon your own
coasts for evidence. I have spoken of the boulder clay and drift as
resting upon the chalk. That is not strictly true. Interposed between the
chalk and the drift is a comparatively insignificant layer, containing
vegetable matter. But that layer tells a wonderful history. It is full of
stumps of trees standing as they grew. Fir-trees are there with their
cones, and hazel-bushes with their nuts; there stand the stools of oak
and yew trees, beeches and alders. Hence this stratum is appropriately
called the "forest-bed."

It is obvious that the chalk must have been upheaved and converted into
dry land, before the timber trees could grow upon it. As the bolls of
some of these trees are from two to three feet in diameter, it is no less
clear that the dry land thus formed remained in the same condition for
long ages. And not only do the remains of stately oaks and well-grown
firs testify to the duration of this condition of things, but additional
evidence to the same effect is afforded by the abundant remains of
elephants, rhinoceroses, hippopotamuses, and other great wild beasts,
which it has yielded to the zealous search of such men as the Rev. Mr.
Gunn. When you look at such a collection as he has formed, and bethink
you that these elephantine bones did veritably carry their owners about,
and these great grinders crunch, in the dark woods of which the forest-
bed is now the only trace, it is impossible not to feel that they are as
good evidence of the lapse of time as the annual rings of the tree

Thus there is a writing upon the wall of cliffs at Cromer, and whoso runs
may read it. It tells us, with an authority which cannot be impeached,
that the ancient sea-bed of the chalk sea was raised up, and remained dry
land, until it was covered with forest, stocked with the great game the
spoils of which have rejoiced your geologists. How long it remained in
that condition cannot be said; but "the whirligig of time brought its
revenges" in those days as in these. That dry land, with the bones and
teeth of generations of long-lived elephants, hidden away among the
gnarled roots and dry leaves of its ancient trees, sank gradually to the
bottom of the icy sea, which covered it with huge masses of drift and
boulder clay. Sea-beasts, such as the walrus, now restricted to the
extreme north, paddled about where birds had twittered among the topmost
twigs of the fir-trees. How long this state of things endured we know
not, but at length it came to an end. The upheaved glacial mud hardened
into the soil of modern Norfolk. Forests grew once more, the wolf and the
beaver replaced the reindeer and the elephant; and at length what we call
the history of England dawned.

Thus you have, within the limits of your own county, proof that the chalk
can justly claim a very much greater antiquity than even the oldest
physical traces of mankind. But we may go further and demonstrate, by
evidence of the same authority as that which testifies to the existence
of the father of men, that the chalk is vastly older than Adam himself.
The Book of Genesis informs us that Adam, immediately upon his creation,
and before the appearance of Eve, was placed in the Garden of Eden. The
problem of the geographical position of Eden has greatly vexed the
spirits of the learned in such matters, but there is one point respecting
which, so far as I know, no commentator has ever raised a doubt. This is,
that of the four rivers which are said to run out of it, Euphrates and
Hiddekel are identical with the rivers now known by the names of
Euphrates and Tigris. But the whole country in which these mighty rivers
take their origin, and through which they run, is composed of rocks which
are either of the same age as the chalk, or of later date. So that the
chalk must not only have been formed, but, after its formation, the time
required for the deposit of these later rocks, and for their upheaval
into dry land, must have elapsed, before the smallest brook which feeds
the swift stream of "the great river, the river of Babylon," began to

Thus, evidence which cannot be rebutted, and which need not be
strengthened, though if time permitted I might indefinitely increase its
quantity, compels you to believe that the earth, from the time of the
chalk to the present day, has been the theatre of a series of changes as
vast in their amount, as they were slow in their progress. The area on
which we stand has been first sea and then land, for at least four
alternations; and has remained in each of these conditions for a period
of great length.

Nor have these wonderful metamorphoses of sea into land, and of land into
sea, been confined to one corner of England. During the chalk period, or
"cretaceous epoch," not one of the present great physical features of the
globe was in existence. Our great mountain ranges, Pyrenees, Alps,
Himalayas, Andes, have all been upheaved since the chalk was deposited,
and the cretaceous sea flowed over the sites of Sinai and Ararat. All
this is certain, because rocks of cretaceous, or still later, date have
shared in the elevatory movements which gave rise to these mountain
chains; and may be found perched up, in some cases, many thousand feet
high upon their flanks. And evidence of equal cogency demonstrates that,
though, in Norfolk, the forest-bed rests directly upon the chalk, yet it
does so, not because the period at which the forest grew immediately
followed that at which the chalk was formed, but because an immense lapse
of time, represented elsewhere by thousands of feet of rock, is not
indicated at Cromer.

I must ask you to believe that there is no less conclusive proof that a
still more prolonged succession of similar changes occurred, before the
chalk was deposited. Nor have we any reason to think that the first term
in the series of these changes is known. The oldest sea-beds preserved to
us are sands, and mud, and pebbles, the wear and tear of rocks which were
formed in still older oceans.

But, great as is the magnitude of these physical changes of the world,
they have been accompanied by a no less striking series of modifications
in its living inhabitants. All the great classes of animals, beasts of
the field, fowls of the air, creeping things, and things which dwell in
the waters, flourished upon the globe long ages before the chalk was
deposited. Very few, however, if any, of these ancient forms of animal
life were identical with those which now live. Certainly not one of the
higher animals was of the same species as any of those now in existence.
The beasts of the field, in the days before the chalk, were not our
beasts of the field, nor the fowls of the air such as those which the eye
of men has seen flying, unless his antiquity dates infinitely further
back than we at present surmise. If we could be carried back into those
times, we should be as one suddenly set down in Australia before it was
colonized. We should see mammals, birds, reptiles, fishes, insects,
snails, and the like, clearly recognizable as such, and yet not one of
them would be just the same as those with which we are familiar, and many
would be extremely different.

From that time to the present, the population of the world has undergone
slow and gradual, but incessant, changes. There has been no grand
catastrophe--no destroyer has swept away the forms of life of one period,
and replaced them by a totally new creation: but one species has vanished
and another has taken its place; creatures of one type of structure have
diminished, those of another have increased, as time has passed on. And
thus, while the differences between the living creatures of the time
before the chalk and those of the present day appear startling, if placed
side by side, we are led from one to the other by the most gradual
progress, if we follow the course of Nature through the whole series of
those relics of her operations which she has left behind. It is by the
population of the chalk sea that the ancient and the modern inhabitants
of the world are most completely connected. The groups which are dying
out flourish, side by side, with the groups which are now the dominant
forms of life. Thus the chalk contains remains of those strange flying
and swimming reptiles, the pterodactyl, the ichthyosaurus, and the
plesiosaurus, which are found in no later deposits, but abounded in
preceding ages. The chambered shells called ammonites and belemnites,
which are so characteristic of the period preceding the cretaceous, in
like manner die with it.

But, amongst these fading remainders of a previous state of things, are
some very modern forms of life, looking like Yankee pedlars among a tribe
of Red Indians. Crocodiles of modern type appear; bony fishes, many of
them very similar to existing species, almost supplant the forms of fish
which predominate in more ancient seas; and many kinds of living shell-
fish first become known to us in the chalk. The vegetation acquires a
modern aspect. A few living animals are not even distinguishable as
species, from those which existed at that remote epoch. The _Globigerina_
of the present day, for example, is not different specifically from that
of the chalk; and the same maybe said of many other _Foraminifera_. I
think it probable that critical and unprejudiced examination will show
that more than one species of much higher animals have had a similar
longevity; but the only example which I can at present give confidently
is the snake's-head lampshell (_Terebratulina caput serpentis_), which
lives in our English seas and abounded (as _Terebratulina striata_ of
authors) in the chalk.

The longest line of human ancestry must hide its diminished head before
the pedigree of this insignificant shell-fish. We Englishmen are proud to
have an ancestor who was present at the Battle of Hastings. The ancestors
of _Terebratulina caput serpentis_ may have been present at a battle of
_Ichthyosauria_ in that part of the sea which, when the chalk was
forming, flowed over the site of Hastings. While all around has changed,
this _Terebratulina_ has peacefully propagated its species from
generation to generation, and stands to this day, as a living testimony
to the continuity of the present with the past history of the globe.

Up to this moment I have stated, so far as I know, nothing but well-
authenticated facts, and the immediate conclusions which they force upon
the mind. But the mind is so constituted that it does not willingly rest
in facts and immediate causes, but seeks always after a knowledge of the
remoter links in the chain of causation.

Taking the many changes of any given spot of the earth's surface, from
sea to land and from land to sea, as an established fact, we cannot
refrain from asking ourselves how these changes have occurred. And when
we have explained them--as they must be explained--by the alternate slow
movements of elevation and depression which have affected the crust of
the earth, we go still further back, and ask, Why these movements?

I am not certain that any one can give you a satisfactory answer to that
question. Assuredly I cannot. All that can be said, for certain, is, that
such movements are part of the ordinary course of nature, inasmuch as
they are going on at the present time. Direct proof may be given, that
some parts of the land of the northern hemisphere are at this moment
insensibly rising and others insensibly sinking; and there is indirect,
but perfectly satisfactory, proof, that an enormous area now covered by
the Pacific has been deepened thousands of feet, since the present
inhabitants of that sea came into existence. Thus there is not a shadow
of a reason for believing that the physical changes of the globe, in past
times, have been effected by other than natural causes. Is there any more
reason for believing that the concomitant modifications in the forms of
the living inhabitants of the globe have been brought about in other

Before attempting to answer this question, let us try to form a distinct
mental picture of what has happened in some special case. The crocodiles
are animals which, as a group, have a very vast antiquity. They abounded
ages before the chalk was deposited; they throng the rivers in warm
climates, at the present day. There is a difference in the form of the
joints of the back-bone, and in some minor particulars, between the
crocodiles of the present epoch and those which lived before the chalk;
but, in the cretaceous epoch, as I have already mentioned, the crocodiles
had assumed the modern type of structure. Notwithstanding this, the
crocodiles of the chalk are not identically the same as those which lived
in the times called "older tertiary," which succeeded the cretaceous
epoch; and the crocodiles of the older tertiaries are not identical with
those of the newer tertiaries, nor are these identical with existing
forms. I leave open the question whether particular species may have
lived on from epoch to epoch. But each epoch has had its peculiar
crocodiles; though all, since the chalk, have belonged to the modern
type, and differ simply in their proportions, and in such structural
particulars as are discernible only to trained eyes.

How is the existence of this long succession of different species of
crocodiles to be accounted for? Only two suppositions seem to be open to
us--Either each species of crocodile has been specially created, or it
has arisen out of some pre-existing form by the operation of natural
causes. Choose your hypothesis; I have chosen mine. I can find no
warranty for believing in the distinct creation of a score of successive
species of crocodiles in the course of countless ages of time. Science
gives no countenance to such a wild fancy; nor can even the perverse
ingenuity of a commentator pretend to discover this sense, in the simple
words in which the writer of Genesis records the proceedings of the fifth
and six days of the Creation.

On the other hand, I see no good reason for doubting the necessary
alternative, that all these varied species have been evolved from pre-
existing crocodilian forms, by the operation of causes as completely a
part of the common order of nature as those which have effected the
changes of the inorganic world. Few will venture to affirm that the
reasoning which applies to crocodiles loses its force among other
animals, or among plants. If one series of species has come into
existence by the operation of natural causes, it seems folly to deny that
all may have arisen in the same way.

A small beginning has led us to a great ending. If I were to put the bit
of chalk with which we started into the hot but obscure flame of burning
hydrogen, it would presently shine like the sun. It seems to me that this
physical metamorphosis is no false image of what has been the result of
our subjecting it to a jet of fervent, though nowise brilliant, thought
to-night. It has become luminous, and its clear rays, penetrating the
abyss of the remote past, have brought within our ken some stages of the
evolution of the earth. And in the shifting "without haste, but without
rest" of the land and sea, as in the endless variation of the forms
assumed by living beings, we have observed nothing but the natural
product of the forces originally possessed by the substance of the




On the 21st of December, 1872, H.M.S. _Challenger_, an eighteen gun
corvette, of 2,000 tons burden, sailed from Portsmouth harbour for a
three, or perhaps four, years' cruise. No man-of-war ever left that
famous port before with so singular an equipment. Two of the eighteen
sixty-eight pounders of the _Challenger's_ armament remained to enable
her to speak with effect to sea-rovers, haply devoid of any respect for
science, in the remote seas for which she is bound; but the main-deck
was, for the most part, stripped of its war-like gear, and fitted up with
physical, chemical, and biological laboratories; Photography had its dark
cabin; while apparatus for dredging, trawling, and sounding; for
photometers and for thermometers, filled the space formerly occupied by
guns and gun-tackle, pistols and cutlasses.

The crew of the _Challenger_ match her fittings. Captain Nares, his
officers and men, are ready to look after the interests of hydrography,
work the ship, and, if need be, fight her as seamen should; while there
is a staff of scientific civilians, under the general direction of Dr.
Wyville Thomson, F.R.S. (Professor of Natural History in Edinburgh
University by rights, but at present detached for duty _in partibus_),
whose business it is to turn all the wonderfully packed stores of
appliances to account, and to accumulate, before the ship returns to
England, such additions to natural knowledge as shall justify the labour
and cost involved in the fitting out and maintenance of the expedition.

Under the able and zealous superintendence of the Hydrographer, Admiral
Richards, every precaution which experience and forethought could devise
has been taken to provide the expedition with the material conditions of
success; and it would seem as if nothing short of wreck or pestilence,
both most improbable contingencies, could prevent the _Challenger_ from
doing splendid work, and opening up a new era in the history of
scientific voyages.

The dispatch of this expedition is the culmination of a series of such
enterprises, gradually increasing in magnitude and importance, which the
Admiralty, greatly to its credit, has carried out for some years past;
and the history of which is given by Dr. Wyville Thomson in the
beautifully illustrated volume entitled "The Depths of the Sea,"
published since his departure.

"In the spring of the year 1868, my friend Dr. W.B. Carpenter, at that
time one of the Vice-Presidents of the Royal Society, was with me in
Ireland, where we were working out together the structure and development
of the Crinoids. I had long previously had a profound conviction that the
land of promise for the naturalist, the only remaining region where there
were endless novelties of extraordinary interest ready to the hand which
had the means of gathering them, was the bottom of the deep sea. I had
even had a glimpse of some of these treasures, for I had seen, the year
before, with Prof. Sars, the forms which I have already mentioned dredged
by his son at a depth of 300 to 400 fathoms off the Loffoten Islands. I
propounded my views to my fellow-labourer, and we discussed the subject
many times over our microscopes. I strongly urged Dr. Carpenter to use
his influence at head-quarters to induce the Admiralty, probably through
the Council of the Royal Society, to give us the use of a vessel properly
fitted with dredging gear and all necessary scientific apparatus, that
many heavy questions as to the state of things in the depths of the
ocean, which were still in a state of uncertainty, might be definitely
settled. After full consideration, Dr. Carpenter promised his hearty co-
operation, and we agreed that I should write to him on his return to
London, indicating generally the results which I anticipated, and
sketching out what I conceived to be a promising line of inquiry. The
Council of the Royal Society warmly supported the proposal; and I give
here in chronological order the short and eminently satisfactory
correspondence which led to the Admiralty placing at the disposal of Dr.
Carpenter and myself the gunboat _Lightninq_, under the command of Staff-
Commander May, R.N., in the summer of 1868, for a trial cruise to the
North of Scotland, and afterwards to the much wider surveys in H.M.S.
_Porcupine_, Captain Calver, R.N., which were made with the additional
association of Mr. Gwyn Jeffreys, in the summers of the years 1869 and

[Footnote 1: The Depths of the Sea, pp. 49-50.]

Plain men may be puzzled to understand why Dr. Wyville Thomson, not being
a cynic, should relegate the "Land of Promise" to the bottom of the deep
sea, they may still more wonder what manner of "milk and honey" the
_Challenger_ expects to find; and their perplexity may well rise to its
maximum, when they seek to divine the manner in which that milk and honey
are to be got out of so inaccessible a Canaan. I will, therefore,
endeavour to give some answer to these questions in an order the reverse
of that in which I have stated them.

Apart from hooks, and lines, and ordinary nets, fishermen have, from time
immemorial, made use of two kinds of implements for getting at sea-
creatures which live beyond tide-marks--these are the "dredge" and the
"trawl." The dredge is used by oyster-fishermen. Imagine a large bag, the
mouth of which has the shape of an elongated parallelogram, and is
fastened to an iron frame of the same shape, the two long sides of this
rim being fashioned into scrapers. Chains attach the ends of the frame to
a stout rope, so that when the bag is dragged along by the rope the edge
of one of the scrapers rests on the ground, and scrapes whatever it
touches into the bag. The oyster-dredger takes one of these machines in
his boat, and when he has reached the oyster-bed the dredge is tossed
overboard; as soon as it has sunk to the bottom the rope is paid out
sufficiently to prevent it from pulling the dredge directly upwards, and
is then made fast while the boat goes ahead. The dredge is thus dragged
along and scrapes oysters and other sea-animals and plants, stones, and
mud into the bag. When the dredger judges it to be full he hauls it up,
picks out the oysters, throws the rest overboard, and begins again.

Dredging in shallow water, say ten to twenty fathoms, is an easy
operation enough; but the deeper the dredger goes, the heavier must be
his vessel, and the stouter his tackle, while the operation of hauling up
becomes more and more laborious. Dredging in 150 fathoms is very hard
work, if it has to be carried on by manual labour; but by the use of the
donkey-engine to supply power,[2] and of the contrivances known as
"accumulators," to diminish the risk of snapping the dredge rope by the
rolling and pitching of the vessel, the dredge has been worked deeper and
deeper, until at last, on the 22nd of July, 1869, H.M.S. _Porcupine_
being in the Bay of Biscay, Captain Calver, her commander, performed the
unprecedented feat of dredging in 2,435 fathoms, or 14,610 feet, a depth
nearly equal to the height of Mont Blanc. The dredge "was rapidly hauled
on deck at one o'clock in the morning of the 23rd, after an absence of
7-1/4 hours, and a journey of upwards of eight statute miles," with a
hundred weight and a half of solid contents.

[Footnote 2: The emotional side of the scientific nature has its
singularities. Many persons will call to mind a certain philosopher's
tenderness over his watch--"the little creature"--which was so singularly
lost and found again. But Dr. Wyville Thomson surpasses the owner of the
watch in his loving-kindness towards a donkey-engine. "This little engine
was the comfort of our lives. Once or twice it was overstrained, and then
we pitied the willing little thing, panting like an overtaxed horse."]

The trawl is a sort of net for catching those fish which habitually live
at the bottom of the sea, such as soles, plaice, turbot, and gurnett. The
mouth of the net may be thirty or forty feet wide, and one edge of its
mouth is fastened to a beam of wood of the same length. The two ends of
the beam are supported by curved pieces of iron, which raise the beam and
the edge of the net which is fastened to it, for a short distance, while
the other edge of the mouth of the net trails upon the ground. The closed
end of the net has the form of a great pouch; and, as the beam is dragged
along, the fish, roused from the bottom by the sweeping of the net,
readily pass into its mouth and accumulate in the pouch at its end. After
drifting with the tide for six or seven hours the trawl is hauled up, the
marketable fish are picked out, the others thrown away, and the trawl
sent overboard for another operation.

More than a thousand sail of well-found trawlers are constantly engaged
in sweeping the seas around our coast in this way, and it is to them that
we owe a very large proportion of our supply of fish. The difficulty of
trawling, like that of dredging, rapidly increases with the depth at
which the operation is performed; and, until the other day, it is
probable that trawling at so great a depth as 100 fathoms was something
unheard of. But the first news from the _Challenger_ opens up new
possibilities for the trawl.

Dr. Wyville Thomson writes ("Nature," March 20, 1873):--

"For the first two or three hauls in very deep water off the coast of
Portugal, the dredge came up filled with the usual 'Atlantic ooze,'
tenacious and uniform throughout, and the work of hours, in sifting, gave
the very smallest possible result. We were extremely anxious to get some
idea of the general character of the Fauna, and particularly of the
distribution of the higher groups; and after various suggestions for
modification of the dredge, it was proposed to try the ordinary trawl. We
had a compact trawl, with a 15-feet beam, on board, and we sent it down
off Cape St. Vincent at a depth of 600 fathoms. The experiment looked
hazardous, but, to our great satisfaction, the trawl came up all right
and contained, with many of the larger invertebrate, several fishes....
After the first attempt we tried the trawl several times at depths of
1090, 1525, and, finally, 2125 fathoms, and always with success."

To the coral-fishers of the Mediterranean, who seek the precious red
coral, which grows firmly fixed to rocks at a depth of sixty to eighty
fathoms, both the dredge and the trawl would be useless. They, therefore,
have recourse to a sort of frame, to which are fastened long bundles of
loosely netted hempen cord, and which is lowered by a rope to the depth
at which the hempen cords can sweep over the surface of the rocks and
break off the coral, which is brought up entangled in the cords. A
similar contrivance has arisen out of the necessities of deep-sea

In the course of the dredging of the _Porcupine_, it was frequently found
that, while few objects of interest were brought up within the dredge,
many living creatures came up sticking to the outside of the dredge-bag,
and even to the first few fathoms of the dredge-rope. The mouth of the
dredge doubtless rapidly filled with mud, and thus the things it should
have brought up were shut out. To remedy this inconvenience Captain
Calver devised an arrangement not unlike that employed by the coral-
fishers. He fastened half a dozen swabs, such as are used for drying
decks, to the dredge. A swab is something like what a birch-broom would
be if its twigs were made of long, coarse, hempen yarns. These dragged
along after the dredge over the surface of the mud, and entangled the
creatures living there--multitudes of which, twisted up in the strands of
the swabs, were brought to the surface with the dredge. A further
improvement was made by attaching a long iron bar to the bottom of the
dredge bag, and fastening large bunches of teased-out hemp to the end of
this bar. These "tangles" bring up immense quantities of such animals as
have long arms, or spines, or prominences which readily become caught in
the hemp, but they are very destructive to the fragile organisms which
they imprison; and, now that the trawl can be successfully worked at the
greatest depths, it may be expected to supersede them; at least, wherever
the ground is soft enough to permit of trawling.

It is obvious that between the dredge, the trawl, and the tangles, there
is little chance for any organism, except such as are able to burrow
rapidly, to remain safely at the bottom of any part of the sea which the
_Challenger_ undertakes to explore. And, for the first time in the
history of scientific exploration, we have a fair chance of learning what
the population of the depths of the sea is like in the most widely
different parts of the world.

And now arises the next question. The means of exploration being fairly
adequate, what forms of life may be looked for at these vast depths?

The systematic study of the Distribution of living beings is the most
modern branch of Biological Science, and came into existence long after
Morphology and Physiology had attained a considerable development. This
naturally does not imply that, from the time men began to observe natural
phenomena, they were ignorant of the fact that the animals and plants of
one part of the world are different from those in other regions; or that
those of the hills are different from those of the plains in the same
region; or finally that some marine creatures are found only in the
shallows, while others inhabit the deeps. Nevertheless, it was only after
the discovery of America that the attention of naturalists was powerfully
drawn to the wonderful differences between the animal population of the
central and southern parts of the new world and that of those parts of
the old world which lie under the same parallels of latitude. So far back
as 1667 Abraham Mylius, in his treatise "De Animalium origine et
migratione, populorum," argues that, since there are innumerable species
of animals in America which do not exist elsewhere, they must have been
made and placed there by the Deity: Buffon no less forcibly insists upon
the difference between the Faunae of the old and new world. But the first
attempt to gather facts of this order into a whole, and to coordinate
them into a series of generalizations, or laws of Geographical
Distribution, is not a century old, and is contained in the "Specimen
Zoologiae Geographicae Quadrupedum Domicilia et Migrationes sistens,"
published, in 1777, by the learned Brunswick Professor, Eberhard
Zimmermann, who illustrates his work by what he calls a "Tabula
Zoographica," which is the oldest distributional map known to me.

In regard to matters of fact, Zimmermann's chief aim is to show that
among terrestrial mammals, some occur all over the world, while others
are restricted to particular areas of greater or smaller extent; and that
the abundance of species follows temperature, being greatest in warm and
least in cold climates. But marine animals, he thinks, obey no such law.
The Arctic and Atlantic seas, he says, are as full of fishes and other
animals as those of the tropics. It is, therefore, clear that cold does
not affect the dwellers in the sea as it does land animals, and that this
must be the case follows from the fact that sea water, "propter varias
quas continet bituminis spiritusque particulas," freezes with much more
difficulty than fresh water. On the other hand, the heat of the
Equatorial sun penetrates but a short distance below the surface of the
ocean. Moreover, according to Zimmermann, the incessant disturbance of
the mass of the sea by winds and tides, so mixes up the warm and the cold
that life is evenly diffused and abundant throughout the ocean.

In 1810, Risso, in his work on the Ichthyology of Nice, laid the
foundation of what has since been termed "bathymetrical" distribution, or
distribution in depth, by showing that regions of the sea bottom of
different depths could be distinguished by the fishes which inhabit them.
There was the _littoral region_ between tide marks with its sand-eels,
pipe fishes, and blennies: the _seaweed region_, extending from low-
water-mark to a depth of 450 feet, with its wrasses, rays, and flat fish;
and the _deep-sea region_, from 450 feet to 1500 feet or more, with
its file-fish, sharks, gurnards, cod, and sword-fish.

More than twenty years later, M.M. Audouin and Milne Edwards carried out
the principle of distinguishing the Faunae of different zones of depth
much more minutely, in their "Recherches pour servir a l'Histoire
Naturelle du Littoral de la France," published in 1832.

They divide the area included between highwater-mark and lowwater-mark of
spring tides (which is very extensive, on account of the great rise and
fall of the tide on the Normandy coast about St. Malo, where their
observations were made) into four zones, each characterized by its
peculiar invertebrate inhabitants. Beyond the fourth region they
distinguish a fifth, which is never uncovered, and is inhabited by
oysters, scallops, and large starfishes and other animals. Beyond this
they seem to think that animal life is absent.[3]

[Footnote 3: "Enfin plus has encore, c'est-a-dire alors loin des cotes,
le fond des eaux ne parait plus etre habite, du moms dans nos mers, par
aucun de ces animaux" (1. c. tom. i. p. 237). The "ces animaux" leaves
the meaning of the authors doubtful.]

Audouin and Milne Edwards were the first to see the importance of the
bearing of a knowledge of the manner in which marine animals are
distributed in depth, on geology. They suggest that, by this means, it
will be possible to judge whether a fossiliferous stratum was formed upon
the shore of an ancient sea, and even to determine whether it was
deposited in shallower or deeper water on that shore; the association of
shells of animals which live in different zones of depth will prove that
the shells have been transported into the position in which they are
found; while, on the other hand, the absence of shells in a deposit will
not justify the conclusion that the waters in which it was formed were
devoid of animal inhabitants, inasmuch as they might have been only too
deep for habitation.

The new line of investigation thus opened by the French naturalists was
followed up by the Norwegian, Sars, in 1835, by Edward Forbes, in our own
country, in 1840,[4] and by Oersted, in Denmark, a few years later. The
genius of Forbes, combined with his extensive knowledge of botany,
invertebrate zoology, and geology, enabled him to do more than any of his
compeers, in bringing the importance of distribution in depth into
notice; and his researches in the Aegean Sea, and still more his
remarkable paper "On the Geological Relations of the existing Fauna and
Flora of the British Isles," published in 1846, in the first volume of
the "Memoirs of the Geological Survey of Great Britain," attracted
universal attention.

[Footnote 4: In the paper in the _Memoirs of the Survey_ cited further
on, Forbes writes:--

"In an essay 'On the Association of Mollusca on the British Coasts,
considered with reference to Pleistocene Geology,' printed in [the
_Edinburgh Academic Annual_ for] 1840, I described the mollusca, as
distributed on our shores and seas, in four great zones or regions,
usually denominated 'The Littoral zone,' 'The region of Laminariae,' 'The
region of Coral-lines,' and 'The region of Corals.' An extensive series
of researches, chiefly conducted by the members of the committee
appointed by the British Association to investigate the marine geology of
Britain by means of the dredge, have not invalidated this classification,
and the researches of Professor Loven, in the Norwegian and Lapland seas,
have borne out their correctness The first two of the regions above
mentioned had been previously noticed by Lamoureux, in his account of the
distribution (vertically) of sea-weeds, by Audouin and Milne Edwards in
their _Observations on the Natural History of the coast of France_, and
by Sars in the preface to his _Beskrivelser og Jagttayelser_."]

On the coasts of the British Islands, Forbes distinguishes four zones or
regions, the Littoral (between tide marks), the Laminarian (between
lowwater-mark and 15 fathoms), the Coralline (from 15 to 50 fathoms), and
the Deep sea or Coral region (from 50 fathoms to beyond 100 fathoms).
But, in the deeper waters of the Aegean Sea, between the shore and a depth
of 300 fathoms, Forbes was able to make out no fewer than eight zones of
life, in the course of which the number and variety of forms gradually
diminished until, beyond 300 fathoms, life disappeared altogether. Hence
it appeared as if descent in the sea had much the same effect on life, as
ascent on land. Recent investigations appear to show that Forbes was
right enough in his classification of the facts of distribution in depth
as they are to be observed in the Aegean; and though, at the time he
wrote, one or two observations were extant which might have warned him
not to generalize too extensively from his Aegean experience, his own
dredging work was so much more extensive and systematic than that of any
other naturalist, that it is not wonderful he should have felt justified
in building upon it. Nevertheless, so far as the limit of the range of
life in depth goes, Forbes' conclusion has been completely negatived, and
the greatest depths yet attained show not even an approach to a "zero of

"During the several cruises of H.M. ships _Lightning_ and _Porcupine_ in
the years 1868, 1869, and 1870," says Dr. Wyville Thomson, "fifty-seven
hauls of the dredge were taken in the Atlantic at depths beyond 500
fathoms, and sixteen at depths beyond 1,000 fathoms, and, in all cases,
life was abundant. In 1869, we took two casts in depths greater than
2,000 fathoms. In both of these life was abundant; and with the deepest
cast, 2,435 fathoms, off the month of the Bay of Biscay, we took living,
well-marked and characteristic examples of all the five invertebrate sub-
kingdoms. And thus the question of the existence of abundant animal life
at the bottom of the sea has been finally settled and for all depths, for
there is no reason to suppose that the depth anywhere exceeds between
three and four thousand fathoms; and if there be nothing in the
conditions of a depth of 2,500 fathoms to prevent the full development of
a varied Fauna, it is impossible to suppose that even an additional
thousand fathoms would make any great difference."[5]

[Footnote 5: _The Depths of the Sea_, p. 30. Results of a similar kind,
obtained by previous observers, are stated at length in the sixth
chapter, pp. 267-280. The dredgings carried out by Count Pourtales, under
the authority of Professor Peirce, the Superintendent of the United
States Coast Survey, in the years 1867, 1868, and 1869, are particularly
noteworthy, and it is probably not too much to say, in the words of
Professor Agassiz, "that we owe to the coast survey the first broad and
comprehensive basis for an exploration of the sea bottom on a large
scale, opening a new era in zoological and geological research."]

As Dr. Wyville Thomson's recent letter, cited above, shows, the use of
the trawl, at great depths, has brought to light a still greater
diversity of life. Fishes came up from a depth of 600 to more than 1,000
fathoms, all in a peculiar condition from the expansion of the air
contained in their bodies. On their relief from the extreme pressure,
their eyes, especially, had a singular appearance, protruding like great
globes from their heads. Bivalve and univalve mollusca seem to be rare at
the greatest depths; but starfishes, sea urchins and other echinoderms,
zoophytes, sponges, and protozoa abound.

It is obvious that the _Challenger_ has the privilege of opening a new
chapter in the history of the living world. She cannot send down her
dredges and her trawls into these virgin depths of the great ocean
without bringing up a discovery. Even though the thing itself may be
neither "rich nor rare," the fact that it came from that depth, in that
particular latitude and longitude, will be a new fact in distribution,
and, as such, have a certain importance.

But it may be confidently assumed that the things brought up will very
frequently be zoological novelties; or, better still, zoological
antiquities, which, in the tranquil and little-changed depths of the
ocean, have escaped the causes of destruction at work in the shallows,
and represent the predominant population of a past age.

It has been seen that Audouin and Milne Edwards foresaw the general
influence of the study of distribution in depth upon the interpretation
of geological phenomena. Forbes connected the two orders of inquiry still
more closely; and in the thoughtful essay "On the connection between the
distribution of the existing Fauna and Flora of the British Isles, and
the geological changes which have affected their area, especially during
the epoch of the Northern drift," to which reference has already been
made, he put forth a most pregnant suggestion.

In certain parts of the sea bottom in the immediate vicinity of the
British Islands, as in the Clyde district, among the Hebrides, in the
Moray Firth, and in the German Ocean, there are depressed areas, forming a
kind of submarine valleys, the centres of which are from 80 to 100
fathoms, or more, deep. These depressions are inhabited by assemblages of
marine animals, which differ from those found over the adjacent and
shallower region, and resemble those which are met with much farther
north, on the Norwegian coast. Forbes called these Scandinavian
detachments "Northern outliers."

How did these isolated patches of a northern population get into these
deep places? To explain the mystery, Forbes called to mind the fact that,
in the epoch which immediately preceded the present, the climate was much
colder (whence the name of "glacial epoch" applied to it); and that the
shells which are found fossil, or sub-fossil, in deposits of that age are
precisely such as are now to be met with only in the Scandinavian, or
still more Arctic, regions. Undoubtedly, during the glacial epoch, the
general population of our seas had, universally, the northern aspect
which is now presented only by the "northern outliers"; just as the
vegetation of the land, down to the sea-level, had the northern character
which is, at present, exhibited only by the plants which live on the tops
of our mountains. But, as the glacial epoch passed away, and the present
climatal conditions were developed, the northern plants were able to
maintain themselves only on the bleak heights, on which southern forms
could not compete with them. And, in like manner, Forbes suggested that,
after the glacial epoch, the northern animals then inhabiting the sea
became restricted to the deeps in which they could hold their own against
invaders from the south, better fitted than they to flourish in the
warmer waters of the shallows. Thus depth in the sea corresponded in its
effect upon distribution to height on the land.

The same idea is applied to the explanation of a similar anomaly in the
Fauna of the Aegean:--

"In the deepest of the regions of depth of the Aegean, the representation
of a Northern Fauna is maintained, partly by identical and partly by
representative forms.... The presence of the latter is essentially due to
the law (of representation of parallels of latitude by zones of depth),
whilst that of the former species depended on their transmission from
their parent seas during a former epoch, and subsequent isolation. That
epoch was doubtless the newer Pliocene or Glacial Era, when the _Mya
truncata_ and other northern forms now extinct in the Mediterranean, and
found fossil in the Sicilian tertiaries, ranged into that sea. The
changes which there destroyed the _shallow water_ glacial forms, did not
affect those living in the depths, and which still survive."[6]

[Footnote 6: _Memoirs of the Geological Survey of Great Britain_, Vol. i.
p. 390.]

The conception that the inhabitants of local depressions of the sea
bottom might be a remnant of the ancient population of the area, which
had held their own in these deep fastnesses against an invading Fauna, as
Britons and Gaels have held out in Wales and in Scotland against
encroaching Teutons, thus broached by Forbes, received a wider
application than Forbes had dreamed of when the sounding machine first
brought up specimens of the mud of the deep sea. As I have pointed out
elsewhere,[7] it at once became obvious that the calcareous sticky mud of
the Atlantic was made up, in the main, of shells of _Globigerina_ and
other _Foraminifera_, identical with those of which the true chalk is
composed, and the identity extended even to the presence of those
singular bodies, the Coccoliths and Coccospheres, the true nature of
which is not yet made out. Here then were organisms, as old as the
cretaceous epoch, still alive, and doing their work of rock-making at the
bottom of existing seas. What if _Globigerina_ and the Coccoliths should
not be the only survivors of a world passed away, which are hidden
beneath three miles of salt water? The letter which Dr. Wyville Thomson
wrote to Dr. Carpenter in May, 1868, out of which all these expeditions
have grown, shows that this query had become a practical problem in Dr.
Thomson's mind at that time; and the desirableness of solving the problem
is put in the foreground of his reasons for urging the Government to
undertake the work of exploration:--

[Footnote 7: See above, "On a Piece of Chalk," p. 13.]

"Two years ago, M. Sars, Swedish Government Inspector of Fisheries, had
an opportunity, in his official capacity, of dredging off the Loffoten
Islands at a depth of 300 fathoms. I visited Norway shortly after his
return, and had an opportunity of studying with his father, Professor
Sars, some of his results. Animal forms were _abundant_; many of them
were new to science; and among them was one of surpassing interest, the
small crinoid, of which you have a specimen, and which we at once
recognised as a degraded type of the _Apiocrinidoe_, an order hitherto
regarded as extinct, which attained its maximum in the Pear Encrinites of
the Jurassic period, and whose latest representative hitherto known was
the _Bourguettocrinus_ of the chalk. Some years previously, Mr.
Absjornsen, dredging in 200 fathoms in the Hardangerfjord, procured
several examples of a Starfish (_Brisinga_), which seems to find its
nearest ally in the fossil genus _Protaster_. These observations place it
beyond a doubt that animal life is abundant in the ocean at depths
varying from 200 to 300 fathoms, that the forms at these great depths
differ greatly from those met with in ordinary dredgings, and that, at
all events in some cases, these animals are closely allied to, and would
seem to be directly descended from, the Fauna of the early tertiaries.

"I think the latter result might almost have been anticipated; and,
probably, further investigation will largely add to this class of data,
and will give us an opportunity of testing our determinations of the
zoological position of some fossil types by an examination of the soft
parts of their recent representatives. The main cause of the destruction,
the migration, and the extreme modification of animal types, appear to be
change of climate, chiefly depending upon oscillations of the earth's
crust. These oscillations do not appear to have ranged, in the Northern
portion of the Northern Hemisphere, much beyond 1,000 feet since the
commencement of the Tertiary Epoch. The temperature of deep waters seems
to be constant for all latitudes at 39 deg.; so that an immense area of the
North Atlantic must have had its conditions unaffected by tertiary or
post-tertiary oscillations."[8]

[Footnote 8: The Depths of the Sea, pp. 51-52.]

As we shall see, the assumption that the temperature of the deep sea is
everywhere 39 deg. F. (4 deg. Cent.) is an error, which Dr. Wyville Thomson
adopted from eminent physical writers; but the general justice of the
reasoning is not affected by this circumstance, and Dr. Thomson's
expectation has been, to some extent, already verified.

Thus besides _Globigerina_, there are eighteen species of deep-sea
_Foraminifera_ identical with species found in the chalk. Imbedded in the
chalky mud of the deep sea, in many localities, are innumerable cup-
shaped sponges, provided with six-rayed silicious spicula, so disposed
that the wall of the cup is formed of a lacework of flinty thread. Not
less abundant, in some parts of the chalk formation, are the fossils
known as _Ventriculites_, well described by Dr. Thomson as "elegant vases
or cups, with branching root-like bases, or groups of regularly or
irregularly spreading tubes delicately fretted on the surface with an
impressed network like the finest lace"; and he adds, "When we compare
such recent forms as _Aphrocallistes, Iphiteon, Holtenia_, and
_Askonema_, with certain series of the chalk _Ventriculites_, there
cannot be the slightest doubt that they belong to the same family--in
some cases to very nearly allied genera."[9]

[Footnote 9: _The Depths of the Sea_, p. 484.]

Professor Duncan finds "several corals from the coast of Portugal more
nearly allied to chalk forms than to any others."

The Stalked Crinoids or Feather Stars, so abundant in ancient times, are
now exclusively confined to the deep sea, and the late explorations have
yielded forms of old affinity, the existence of which has hitherto been
unsuspected. The general character of the group of star fishes imbedded
in the white chalk is almost the same as in the modern Fauna of the deep
Atlantic. The sea urchins of the deep sea, while none of them are
specifically identical with any chalk form, belong to the same general
groups, and some closely approach extinct cretaceous genera.

Taking these facts in conjunction with the positive evidence of the
existence, during the Cretaceous epoch, of a deep ocean where now lies
the dry land of central and southern Europe, northern Africa, and western
and southern Asia; and of the gradual diminution of this ocean during the
older tertiary epoch, until it is represented at the present day by such
teacupfuls as the Caspian, the Black Sea, and the Mediterranean; the
supposition of Dr. Thomson and Dr. Carpenter that what is now the deep
Atlantic, was the deep Atlantic (though merged in a vast easterly
extension) in the Cretaceous epoch, and that the _Globigerina_ mud has
been accumulating there from that time to this, seems to me to have a
great degree of probability. And I agree with Dr. Wyville Thomson against
Sir Charles Lyell (it takes two of us to have any chance against his
authority) in demurring to the assertion that "to talk of chalk having
been uninterruptedly formed in the Atlantic is as inadmissible in a
geographical as in a geological sense."

If the word "chalk" is to be used as a stratigraphical term and
restricted to _Globigerina_ mud deposited during the Cretaceous epoch, of
course it is improper to call the precisely similar mud of more recent
date, chalk. If, on the other hand, it is to be used as a mineralogical
term, I do not see how the modern and the ancient chalks are to be
separated--and, looking at the matter geographically, I see no reason to
doubt that a boring rod driven from the surface of the mud which forms
the floor of the mid-Atlantic would pass through one continuous mass of
_Globigerina_ mud, first of modern, then of tertiary, and then of
mesozoic date; the "chalks" of different depths and ages being
distinguished merely by the different forms of other organisms associated
with the _Globigerinoe_.

On the other hand, I think it must be admitted that a belief in the
continuity of the modern with the ancient chalk has nothing to do with
the proposition that we can, in any sense whatever, be said to be still
living in the Cretaceous epoch. When the _Challenger's_ trawl brings up
an _Ichthyosaurus_, along with a few living specimens of _Belemnites_ and
_Turrilites_, it may be admitted that she has come upon a cretaceous
"outlier." A geological period is characterized not only by the presence
of those creatures which lived in it, but by the absence of those which
have only come into existence later; and, however large a proportion of
true cretaceous forms may be discovered in the deep sea, the modern types
associated with them must be abolished before the Fauna, as a whole,
could, with any propriety, be termed Cretaceous.

I have now indicated some of the chief lines of Biological inquiry, in
which the _Challenger_ has special opportunities for doing good service,
and in following which she will be carrying out the work already
commenced by the _Lightning_ and _Porcupine_ in their cruises of 1868 and
subsequent years.

But biology, in the long run, rests upon physics, and the first condition
for arriving at a sound theory of distribution in the deep sea, is the
precise ascertainment of the conditions of life; or, in other words, a
full knowledge of all those phenomena which are embraced under the head
of the Physical Geography of the Ocean.

Excellent work has already been done in this direction, chiefly under the
superintendence of Dr. Carpenter, by the _Lightning_ and the
_Porcupine_,[10] and some data of fundamental importance to the physical
geography of the sea have been fixed beyond a doubt.

[Footnote 10: _Proceedings of the Royal Society_, 1870 and 1872]

Thus, though it is true that sea-water steadily contracts as it cools
down to its freezing point, instead of expanding before it reaches its
freezing point as fresh water does, the truth has been steadily ignored
by even the highest authorities in physical geography, and the erroneous
conclusions deduced from their erroneous premises have been widely
accepted as if they were ascertained facts. Of course, if sea-water, like
fresh water, were heaviest at a temperature of 39 deg. F. and got lighter as
it approached 32 deg. F., the water of the bottom of the deep sea could not
be colder than 39 deg.. But one of the first results of the careful
ascertainment of the temperature at different depths, by means of
thermometers specially contrived for the avoidance of the errors produced
by pressure, was the proof that, below 1000 fathoms in the Atlantic, down
to the greatest depths yet sounded, the water has a temperature always
lower than 38 deg. Fahr., whatever be the temperature of the water at the
surface. And that this low temperature of the deepest water is probably
the universal rule for the depths of the open ocean is shown, among
others, by Captain Chimmo's recent observations in the Indian ocean,
between Ceylon and Sumatra, where, the surface water ranging from 85 deg.-81 deg.
Fahr., the temperature at the bottom, at a depth of 2270 to 2656 fathoms,
was only from 34 deg. to 32 deg. Fahr.

As the mean temperature of the superficial layer of the crust of the
earth may be taken at about 50 deg. Fahr., it follows that the bottom layer
of the deep sea in temperate and hot latitudes, is, on the average, much
colder than either of the bodies with which it is in contact; for the
temperature of the earth is constant, while that of the air rarely falls
so low as that of the bottom water in the latitudes in question; and even
when it does, has time to affect only a comparatively thin stratum of the
surface water before the return of warm weather.

How does this apparently anomalous state of things come about? If we
suppose the globe to be covered with a universal ocean, it can hardly be
doubted that the cold of the regions towards the poles must tend to cause
the superficial water of those regions to contract and become
specifically heavier. Under these circumstances, it would have no
alternative but to descend and spread over the sea bottom, while its
place would be taken by warmer water drawn from the adjacent regions.
Thus, deep, cold, polar-equatorial currents, and superficial, warmer,
equatorial-polar currents, would be set up; and as the former would have
a less velocity of rotation from west to east than the regions towards
which they travel, they would not be due southerly or northerly currents,
but south-westerly in the northern hemisphere, and north-westerly in the
southern; while, by a parity of reasoning, the equatorial-polar warm
currents would be north-easterly in the northern hemisphere, and south-
easterly in the southern. Hence, as a north-easterly current has the same
direction as a south-westerly wind, the direction of the northern
equatorial-polar current in the extra-tropical part of its course would
pretty nearly coincide with that of the anti-trade winds. The freezing of
the surface of the polar sea would not interfere with the movement thus
set up. For, however bad a conductor of heat ice may be, the unfrozen
sea-water immediately in contact with the undersurface of the ice must
needs be colder than that further off; and hence will constantly tend to
descend through the subjacent warmer water.

In this way, it would seem inevitable that the surface waters of the
northern and southern frigid zones must, sooner or later, find their way
to the bottom of the rest of the ocean; and there accumulate to a
thickness dependent on the rate at which they absorb heat from the crust
of the earth below, and from the surface water above.

If this hypothesis be correct, it follows that, if any part of the ocean
in warm latitudes is shut off from the influence of the cold polar
underflow, the temperature of its deeps should be less cold than the
temperature of corresponding depths in the open sea. Now, in the
Mediterranean, Nature offers a remarkable experimental proof of just the
kind needed. It is a landlocked sea which runs nearly east and west,
between the twenty-ninth and forty-fifth parallels of north latitude.
Roughly speaking, the average temperature of the air over it is 75 deg. Fahr.
in July and 48 deg. in January.

This great expanse of water is divided by the peninsula of Italy
(including Sicily), continuous with which is a submarine elevation
carrying less than 1,200 feet of water, which extends from Sicily to Cape
Bon in Africa, into two great pools--an eastern and a western. The
eastern pool rapidly deepens to more than 12,000 feet, and sends off to
the north its comparatively shallow branches, the Adriatic and the Aegean
Seas. The western pool is less deep, though it reaches some 10,000 feet.
And, just as the western end of the eastern pool communicates by a
shallow passage, not a sixth of its greatest depth, with the western
pool, so the western pool is separated from the Atlantic by a ridge which
runs between Capes Trafalgar and Spartel, on which there is hardly 1,000
feet of water. All the water of the Mediterranean which lies deeper than
about 150 fathoms, therefore, is shut off from that of the Atlantic, and
there is no communication between the cold layer of the Atlantic (below
1,000 fathoms) and the Mediterranean. Under these circumstances, what is
the temperature of the Mediterranean? Everywhere below 600 feet it is
about 55 deg. Fahr.; and consequently, at its greatest depths, it is some 20 deg.
warmer than the corresponding depths of the Atlantic.

It seems extremely difficult to account for this difference in any other
way, than by adopting the views so strongly and ably advocated by Dr.
Carpenter, that, in the existing distribution of land and water, such a
circulation of the water of the ocean does actually occur, as
theoretically must occur, in the universal ocean, with which we started.

It is quite another question, however, whether this theoretic
circulation, true cause as it may be, is competent to give rise to such
movements of sea-water, in mass, as those currents, which have commonly
been regarded as northern extensions of the Gulf-stream. I shall not
venture to touch upon this complicated problem; but I may take occasion
to remark that the cause of a much simpler phenomenon--the stream of
Atlantic water which sets through the Straits of Gibraltar, eastward, at
the rate of two or three miles an hour or more, does not seem to be so
clearly made out as is desirable.

The facts appear to be that the water of the Mediterranean is very
slightly denser than that of the Atlantic (1.0278 to 1.0265), and that
the deep water of the Mediterranean is slightly denser than that of the
surface; while the deep water of the Atlantic is, if anything, lighter
than that of the surface. Moreover, while a rapid superficial current is
setting in (always, save in exceptionally violent easterly winds) through
the Straits of Gibraltar, from the Atlantic to the Mediterranean, a deep
undercurrent (together with variable side currents) is setting out
through the Straits, from the Mediterranean to the Atlantic.

Dr. Carpenter adopts, without hesitation, the view that the cause of this
indraught of Atlantic water is to be sought in the much more rapid
evaporation which takes place from the surface of the Mediterranean than
from that of the Atlantic; and thus, by lowering the level of the former,
gives rise to an indraught from the latter.

But is there any sound foundation for the three assumptions involved
here? Firstly, that the evaporation from the Mediterranean, as a whole,
is much greater than that from the Atlantic under corresponding
parallels; secondly, that the rainfall over the Mediterranean makes up
for evaporation less than it does over the Atlantic; and thirdly,
supposing these two questions answered affirmatively: Are not these
sources of loss in the Mediterranean fully covered by the prodigious
quantity of fresh water which is poured into it by great rivers and
submarine springs? Consider that the water of the Ebro, the Rhine, the
Po, the Danube, the Don, the Dnieper, and the Nile, all flow directly or
indirectly into the Mediterranean; that the volume of fresh water which
they pour into it is so enormous that fresh water may sometimes be baled
up from the surface of the sea off the Delta of the Nile, while the land
is not yet in sight; that the water of the Black Sea is half fresh, and
that a current of three or four miles an hour constantly streams from it
Mediterraneanwards through the Bosphorus;--consider, in addition, that no
fewer than ten submarine springs of fresh water are known to burst up in
the Mediterranean, some of them so large that Admiral Smyth calls them
"subterranean rivers of amazing volume and force"; and it would seem, on
the face of the matter, that the sun must have enough to do to keep the
level of the Mediterranean down; and that, possibly, we may have to seek
for the cause of the small superiority in saline contents of the
Mediterranean water in some condition other than solar evaporation.

Again, if the Gibraltar indraught is the effect of evaporation, why does
it go on in winter as well as in summer?

All these are questions more easily asked than answered; but they must be
answered before we can accept the Gibraltar stream as an example of a
current produced by indraught with any comfort.

The Mediterranean is not included in the _Challenger's_ route, but she
will visit one of the most promising and little explored of
hydrographical regions--the North Pacific, between Polynesia and the
Asiatic and American shores; and doubtless the store of observations upon
the currents of this region, which she will accumulate, when compared
with what we know of the North Atlantic, will throw a powerful light upon
the present obscurity of the Gulf-stream problem.




In May, 1873, I drew attention[1] to the important problems connected
with the physics and natural history of the sea, to the solution of which
there was every reason to hope the cruise of H.M.S. _Challenger_ would
furnish important contributions. The expectation then expressed has not
been disappointed. Reports to the Admiralty, papers communicated to the
Royal Society, and large collections which have already been sent home,
have shown that the _Challenger's_ staff have made admirable use of their
great opportunities; and that, on the return of the expedition in 1874,
their performance will be fully up to the level of their promise. Indeed,
I am disposed to go so far as to say, that if nothing more came of the
_Challengers_ expedition than has hitherto been yielded by her
exploration of the nature of the sea bottom at great depths, a full
scientific equivalent of the trouble and expense of her equipment would
have been obtained.

[Footnote 1: See the preceding Essay.]

In order to justify this assertion, and yet, at the same time, not to
claim more for Professor Wyville Thomson and his colleagues than is their
due, I must give a brief history of the observations which have preceded
their exploration of this recondite field of research, and endeavour to
make clear what was the state of knowledge in December, 1872, and what
new facts have been added by the scientific staff of the _Challenger_. So
far as I have been able to discover, the first successful attempt to
bring up from great depths more of the sea bottom than would adhere to a
sounding-lead, was made by Sir John Ross, in the voyage to the Arctic
regions which he undertook in 1818. In the Appendix to the narrative of
that voyage, there will be found an account of a very ingenious apparatus
called "clams"--a sort of double scoop--of his own contrivance, which Sir
John Ross had made by the ship's armourer; and by which, being in
Baffin's Bay, in 72 deg. 30' N. and 77 deg. 15' W., he succeeded in bringing up
from 1,050 fathoms (or 6,300 feet), "several pounds" of a "fine green
mud," which formed the bottom of the sea in this region. Captain (now Sir
Edward) Sabine, who accompanied Sir John Ross on this cruise, says of
this mud that it was "soft and greenish, and that the lead sunk several
feet into it." A similar "fine green mud" was found to compose the sea
bottom in Davis Straits by Goodsir in 1845. Nothing is certainly known of
the exact nature of the mud thus obtained, but we shall see that the mud
of the bottom of the Antarctic seas is described in curiously similar
terms by Dr. Hooker, and there is no doubt as to the composition of this

In 1850, Captain Penny collected in Assistance Bay, in Kingston Bay, and
in Melville Bay, which lie between 73 deg. 45' and 74 deg. 40' N., specimens of
the residuum left by melted surface ice, and of the sea bottom in these
localities. Dr. Dickie, of Aberdeen, sent these materials to Ehrenberg,
who made out[2] that the residuum of the melted ice consisted for the
most part of the silicious cases of diatomaceous plants, and of the
silicious spicula of sponges; while, mixed with these, were a certain
number of the equally silicious skeletons of those low animal organisms,
which were termed _Polycistineoe_ by Ehrenberg, but are now known as

[Footnote 2: _Ueber neue Anschauungen des kleinsten noerdlichen
Polarlebens_.--Monatsberichte d. K. Akad. Berlin, 1853.]

In 1856, a very remarkable addition to our knowledge of the nature of the
sea bottom in high northern latitudes was made by Professor Bailey of
West Point. Lieutenant Brooke, of the United States Navy, who was
employed in surveying the Sea of Kamschatka, had succeeded in obtaining
specimens of the sea bottom from greater depths than any hitherto
reached, namely from 2,700 fathoms (16,200 feet) in 56 deg. 46' N., and 168 deg.
18' E.; and from 1,700 fathoms (10,200 feet) in 60 deg. 15' N. and 170 deg. 53'
E. On examining these microscopically, Professor Bailey found, as
Ehrenberg had done in the case of mud obtained on the opposite side of
the Arctic region, that the fine mud was made up of shells of
_Diatomacoe_, of spicula of sponges, and of _Radiolaria_, with a small
admixture of mineral matters, but without a trace of any calcareous

Still more complete information has been obtained concerning the nature
of the sea bottom in the cold zone around the south pole. Between the
years 1839 and 1843, Sir James Clark Ross executed his famous Antarctic
expedition, in the course of which he penetrated, at two widely distant
points of the Antarctic zone, into the high latitudes of the shores of
Victoria Land and of Graham's Land, and reached the parallel of 80 deg. S.
Sir James Ross was himself a naturalist of no mean acquirements, and Dr.
Hooker,[3] the present President of the Royal Society, accompanied him as
naturalist to the expedition, so that the observations upon the fauna and
flora of the Antarctic regions made during this cruise were sure to have
a peculiar value and importance, even had not the attention of the
voyagers been particularly directed to the importance of noting the
occurrence of the minutest forms of animal and vegetable life in the

[Footnote 3: Now Sir Joseph Hooker. 1894.]

Among the scientific instructions for the voyage drawn up by a committee
of the Royal Society, however, there is a remarkable letter from Von
Humboldt to Lord Minto, then First Lord of the Admiralty, in which, among
other things, he dwells upon the significance of the researches into the
microscopic composition of rocks, and the discovery of the great share
which microscopic organisms take in the formation of the crust of the
earth at the present day, made by Ehrenberg in the years 1836-39.
Ehrenberg, in fact, had shown that the extensive beds of "rotten-stone"
or "Tripoli" which occur in various parts of the world, and notably at
Bilin in Bohemia, consisted of accumulations of the silicious cases and
skeletons of _Diatomaceoe_, sponges, and _Radiolaria_; he had proved that
similar deposits were being formed by _Diatomaceoe_, in the pools of the
Thiergarten in Berlin and elsewhere, and had pointed out that, if it were
commercially worth while, rotten-stone might be manufactured by a process
of diatom-culture. Observations conducted at Cuxhaven in 1839, had
revealed the existence, at the surface of the waters of the Baltic, of
living Diatoms and _Radiolaria_ of the same species as those which, in a
fossil state, constitute extensive rocks of tertiary age at Caltanisetta,
Zante, and Oran, on the shores of the Mediterranean.

Moreover, in the fresh-water rotten-stone beds of Bilin, Ehrenberg had
traced out the metamorphosis, effected apparently by the action of
percolating water, of the primitively loose and friable deposit of
organized particles, in which the silex exists in the hydrated or soluble
condition. The silex, in fact, undergoes solution and slow redeposition,
until, in ultimate result, the excessively fine-grained sand, each
particle of which is a skeleton, becomes converted into a dense opaline
stone, with only here and there an indication of an organism.

From the consideration of these facts, Ehrenberg, as early as the year
1839, had arrived at the conclusion that rocks, altogether similar to
those which constitute a large part of the crust of the earth, must be
forming, at the present day, at the bottom of the sea; and he threw out
the suggestion that even where no trace of organic structure is to be
found in the older rocks, it may have been lost by metamorphosis.[4]

[Footnote 4: _Ueber die noch jetzt zahlreich lebende Thierarten der
Kreidebildung und den Organismus der Polythalamien. Abhandlungen der Koen.
Akad. der Wissenchaften._ 1839. _Berlin_. 1841. I am afraid that this
remarkable paper has been somewhat overlooked in the recent discussions
of the relation of ancient rocks to modern deposits.]

The results of the Antarctic exploration, as stated by Dr. Hooker in the
"Botany of the Antarctic Voyage," and in a paper which he read before
the British Association in 1847, are of the greatest importance in
connection with these views, and they are so clearly stated in the former
work, which is somewhat inaccessible, that I make no apology for quoting
them at length--

"The waters and the ice of the South Polar Ocean were alike found to
abound with microscopic vegetables belonging to the order _Diatomaceoe_.
Though much too small to be discernible by the naked eye, they occurred
in such countless myriads as to stain the berg and the pack ice wherever
they were washed by the swell of the sea; and, when enclosed in the
congealing surface of the water, they imparted to the brash and pancake
ice a pale ochreous colour. In the open ocean, northward of the frozen
zone, this order, though no doubt almost universally present, generally
eludes the search of the naturalist; except when its species are
congregated amongst that mucous scum which is sometimes seen floating on

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