Part 5 out of 5
like a stroke of lightning," and for a moment made him believe
that "he was done for." Continuing his experiments, nevertheless,
he found that if the jar were placed on a piece of metal on the
table, a shock would be received by touching this piece of metal
with one hand and touching the wire with the other--that is, a
path was made for the electrical discharge through the body. This
was practically the same experiment as made by Von Kleist with
his bottle and nail, but carried one step farther, as it showed
that the "jar" need not necessarily be held in the hand, as
believed by Von Kleist. Further experiments, continued by many
philosophers at the time, revealed what Von Kleist had already
pointed out, that the electrified jar remained charged for some
Soon after this Daniel Gralath, wishing to obtain stronger
discharges than could be had from a single Leyden jar, conceived
the idea of combining several jars, thus for the first time
grouping the generators in a "battery" which produced a discharge
strong enough to kill birds and small animals. He also attempted
to measure the strength of the discharges, but soon gave it up in
despair, and the solution of this problem was left for late
The advent of the Leyden jar, which made it possible to produce
strong electrical discharges from a small and comparatively
simple device, was followed by more spectacular demonstrations of
various kinds all over Europe. These exhibitions aroused the
interest of the kings and noblemen, so that electricity no longer
remained a "plaything of the philosophers" alone, but of kings as
well. A favorite demonstration was that of sending the electrical
discharge through long lines of soldiers linked together by
pieces of wire, the discharge causing them to "spring into the
air simultaneously" in a most astonishing manner. A certain monk
in Paris prepared a most elaborate series of demonstrations for
the amusement of the king, among other things linking together an
entire regiment of nine hundred men, causing them to perform
simultaneous springs and contortions in a manner most amusing to
the royal guests. But not all the experiments being made were of
a purely spectacular character, although most of them
accomplished little except in a negative way. The famous Abbe
Nollet, for example, combined useful experiments with spectacular
demonstrations, thus keeping up popular interest while aiding the
cause of scientific electricity.
Naturally, the new discoveries made necessary a new nomenclature,
new words and electrical terms being constantly employed by the
various writers of that day. Among these writers was the English
scientist William Watson, who was not only a most prolific writer
but a tireless investigator. Many of the words coined by him are
now obsolete, but one at least, "circuit," still remains in use.
In 1746, a French scientist, Louis Guillaume le Monnier, bad made
a circuit including metal and water by laying a chain half-way
around the edge of a pond, a man at either end holding it. One of
these men dipped his free hand in the water, the other presenting
a Leyden jar to a rod suspended on a cork float on the water,
both men receiving a shock simultaneously. Watson, a year later,
attempted the same experiment on a larger scale. He laid a wire
about twelve hundred feet long across Westminster Bridge over the
Thames, bringing the ends to the water's edge on the opposite
banks, a man at one end holding the wire and touching the water.
A second man on the opposite side held the wire and a Leyden jar;
and a third touched the jar with one hand, while with the other
he grasped a wire that extended into the river. In this way they
not only received the shock, but fired alcohol as readily across
the stream as could be done in the laboratory. In this experiment
Watson discovered the superiority of wire over chain as a
conductor, rightly ascribing this superiority to the continuity
of the metal.
Watson continued making similar experiments over longer
watercourses, some of them as long as eight thousand feet, and
while engaged in making one of these he made the discovery so
essential to later inventions, that the earth could be used as
part of the circuit in the same manner as bodies of water.
Lengthening his wires he continued his experiments until a
circuit of four miles was made, and still the electricity seemed
to traverse the course instantaneously, and with apparently
undiminished force, if the insulation was perfect.
Watson's writings now carried the field of active discovery
across the Atlantic, and for the first time an American scientist
appeared--a scientist who not only rivalled, but excelled, his
European contemporaries. Benjamin Franklin, of Philadelphia,
coming into possession of some of Watson's books, became so
interested in the experiments described in them that he began at
once experimenting with electricity. In Watson's book were given
directions for making various experiments, and these assisted
Franklin in repeating the old experiments, and eventually adding
new ones. Associated with Franklin, and equally interested and
enthusiastic, if not equally successful in making discoveries,
were three other men, Thomas Hopkinson, Philip Sing, and Ebenezer
Kinnersley. These men worked together constantly, although it
appears to have been Franklin who made independently the
important discoveries, and formulated the famous Franklinian
Working steadily, and keeping constantly in touch with the
progress of the European investigators, Franklin soon made some
experiments which he thought demonstrated some hitherto unknown
phases of electrical manifestation. This was the effect of
pointed bodies "in DRAWING OFF and THROWING OFF the electrical
fire." In his description of this phenomenon, Franklin writes:
"Place an iron shot of three or four inches diameter on the mouth
of a clean, dry, glass bottle. By a fine silken thread from the
ceiling right over the mouth of the bottle, suspend a small cork
ball, about the bigness of a marble; the thread of such a length
that the cork ball may rest against the side of the shot.
Electrify the shot, and the ball will be repelled to the distance
of four or five inches, more or less, according to the quantity
of electricity. When in this state, if you present to the shot
the point of a long, slender shaft-bodkin, at six or eight inches
distance, the repellency is instantly destroyed, and the cork
flies to the shot. A blunt body must be brought within an inch,
and draw a spark, to produce the same effect.
"To prove that the electrical fire is DRAWN OFF by the point, if
you take the blade of the bodkin out of the wooden handle and fix
it in a stick of sealing-wax, and then present it at the distance
aforesaid, or if you bring it very near, no such effect follows;
but sliding one finger along the wax till you touch the blade,
and the ball flies to the shot immediately. If you present the
point in the dark you will see, sometimes at a foot distance, and
more, a light gather upon it like that of a fire-fly or
glow-worm; the less sharp the point, the nearer you must bring it
to observe the light; and at whatever distance you see the light,
you may draw off the electrical fire and destroy the repellency.
If a cork ball so suspended be repelled by the tube, and a point
be presented quick to it, though at a considerable distance, 'tis
surprising to see how suddenly it flies back to the tube. Points
of wood will do as well as those of iron, provided the wood is
not dry; for perfectly dry wood will no more conduct electricity
"To show that points will THROW OFF as well as DRAW OFF the
electrical fire, lay a long, sharp needle upon the shot, and you
cannot electrify the shot so as to make it repel the cork ball.
Or fix a needle to the end of a suspended gun-barrel or iron rod,
so as to point beyond it like a little bayonet, and while it
remains there, the gun-barrel or rod cannot, by applying the tube
to the other end, be electrified so as to give a spark, the fire
continually running out silently at the point. In the dark you
may see it make the same appearance as it does in the case before
Von Guericke, Hauksbee, and Gray had noticed that pointed bodies
attracted electricity in a peculiar manner, but this
demonstration of the "drawing off" of "electrical fire" was
original with Franklin. Original also was the theory that he now
suggested, which had at least the merit of being thinkable even
by non-philosophical minds. It assumes that electricity is like a
fluid, that will flow along conductors and accumulate in proper
receptacles, very much as ordinary fluids do. This conception is
probably entirely incorrect, but nevertheless it is likely to
remain a popular one, at least outside of scientific circles, or
until something equally tangible is substituted.
FRANKLIN'S THEORY OF ELECTRICITY
According to Franklin's theory, electricity exists in all bodies
as a "common stock," and tends to seek and remain in a state of
equilibrium, just as fluids naturally tend to seek a level. But
it may, nevertheless, be raised or lowered, and this equilibrium
be thus disturbed. If a body has more electricity than its normal
amount it is said to be POSITIVELY electrified; but if it has
less, it is NEGATIVELY electrified. An over-electrified or "plus"
body tends to give its surplus stock to a body containing the
normal amount; while the "minus" or under-electrified body will
draw electricity from one containing the normal amount.
Working along lines suggested by this theory, Franklin attempted
to show that electricity is not created by friction, but simply
collected from its diversified state, the rubbed glass globe
attracting a certain quantity of "electrical fire," but ever
ready to give it up to any body that has less. He explained the
charged Leyden jar by showing that the inner coating of tin-foil
received more than the ordinary quantity of electricity, and in
consequence is POSITIVELY electrified, while the outer coating,
having the ordinary quantity of electricity diminished, is
These studies of the Leyden jar, and the studies of pieces of
glass coated with sheet metal, led Franklin to invent his
battery, constructed of eleven large glass plates coated with
sheets of lead. With this machine, after overcoming some defects,
he was able to produce electrical manifestations of great
force--a force that "knew no bounds," as he declared ("except in
the matter of expense and of labor"), and which could be made to
exceed "the greatest know effects of common lightning."
This reference to lightning would seem to show Franklin's belief,
even at that time, that lightning is electricity. Many eminent
observers, such as Hauksbee, Wall, Gray, and Nollet, had noticed
the resemblance between electric sparks and lightning, but none
of these had more than surmised that the two might be identical.
In 1746, the surgeon, John Freke, also asserted his belief in
this identity. Winkler, shortly after this time, expressed the
same belief, and, assuming that they were the same, declared that
"there is no proof that they are of different natures"; and still
he did not prove that they were the same nature.
FRANKLIN INVENTS THE LIGHTNING-ROD
Even before Franklin proved conclusively the nature of lightning,
his experiments in drawing off the electric charge with points
led to some practical suggestions which resulted in the invention
of the lightning-rod. In the letter of July, 1750, which he wrote
on the subject, he gave careful instructions as to the way in
which these rods might be constructed. In part Franklin wrote:
"May not the knowledge of this power of points be of use to
mankind in preserving houses, churches, ships, etc., from the
stroke of lightning by directing us to fix on the highest parts
of the edifices upright rods of iron made sharp as a needle, and
gilt to prevent rusting, and from the foot of these rods a wire
down the outside of the building into the grounds, or down round
one of the shrouds of a ship and down her side till it reaches
the water? Would not these pointed rods probably draw the
electrical fire silently out of a cloud before it came nigh
enough to strike, and thereby secure us from that most sudden and
"To determine this question, whether the clouds that contain the
lightning are electrified or not, I propose an experiment to be
tried where it may be done conveniently. On the top of some high
tower or steeple, place a kind of sentry-box, big enough to
contain a man and an electrical stand. From the middle of the
stand let an iron rod rise and pass, bending out of the door, and
then upright twenty or thirty feet, pointed very sharp at the
end. If the electrical stand be kept clean and dry, a man
standing on it when such clouds are passing low might be
electrified and afford sparks, the rod drawing fire to him from a
cloud. If any danger to the man be apprehended (though I think
there would be none), let him stand on the floor of his box and
now and then bring near to the rod the loop of a wire that has
one end fastened to the leads, he holding it by a wax handle; so
the sparks, if the rod is electrified, will strike from the rod
to the wire and not effect him."
Not satisfied with all the evidence that he had collected
pointing to the identity of lightning and electricity, he adds
one more striking and very suggestive piece of evidence.
Lightning was known sometimes to strike persons blind without
killing them. In experimenting on pigeons and pullets with his
electrical machine, Franklin found that a fowl, when not killed
outright, was sometimes rendered blind. The report of these
experiments were incorporated in this famous letter of the
The attitude of the Royal Society towards this clearly stated
letter, with its useful suggestions, must always remain as a blot
on the record of this usually very receptive and liberal-minded
body. Far from publishing it or receiving it at all, they derided
the whole matter as too visionary for discussion by the society.
How was it possible that any great scientific discovery could be
made by a self-educated colonial newspaper editor, who knew
nothing of European science except by hearsay, when all the great
scientific minds of Europe had failed to make the discovery? How
indeed! And yet it would seem that if any of the influential
members of the learned society had taken the trouble to read over
Franklin's clearly stated letter, they could hardly have failed
to see that his suggestions were worthy of consideration. But at
all events, whether they did or did not matters little. The fact
remains that they refused to consider the paper seriously at the
time; and later on, when its true value became known, were
obliged to acknowledge their error by a tardy report on the
already well-known document.
But if English scientists were cold in their reception of
Franklin's theory and suggestions, the French scientists were
not. Buffon, perceiving at once the importance of some of
Franklin's experiments, took steps to have the famous letter
translated into French, and soon not only the savants, but
members of the court and the king himself were intensely
interested. Two scientists, De Lor and D'Alibard, undertook to
test the truth of Franklin's suggestions as to pointed rods
"drawing off lightning." In a garden near Paris, the latter
erected a pointed iron rod fifty feet high and an inch in
diameter. As no thunder-clouds appeared for several days, a guard
was stationed, armed with an insulated brass wire, who was
directed to test the iron rods with it in case a storm came on
during D'Alibard's absence. The storm did come on, and the guard,
not waiting for his employer's arrival, seized the wire and
touched the rod. Instantly there was a report. Sparks flew and
the guard received such a shock that he thought his time had
come. Believing from his outcry that he was mortally hurt, his
friends rushed for a spiritual adviser, who came running through
rain and hail to administer the last rites; but when he found the
guard still alive and uninjured, he turned his visit to account
by testing the rod himself several times, and later writing a
report of his experiments to M. d'Alibard. This scientist at once
reported the affair to the French Academy, remarking that
"Franklin's idea was no longer a conjecture, but a reality."
FRANKLIN PROVES THAT LIGHTNING IS ELECTRICITY
Europe, hitherto somewhat sceptical of Franklin's views, was by
this time convinced of the identity of lightning and electricity.
It was now Franklin's turn to be sceptical. To him the fact that
a rod, one hundred feet high, became electrified during a storm
did not necessarily prove that the storm-clouds were electrified.
A rod of that length was not really projected into the cloud, for
even a very low thunder-cloud was more than a hundred feet above
the ground. Irrefutable proof could only be had, as he saw it, by
"extracting" the lightning with something actually sent up into
the storm-cloud; and to accomplish this Franklin made his silk
kite, with which he finally demonstrated to his own and the
world's satisfaction that his theory was correct.
Taking his kite out into an open common on the approach of a
thunder-storm, he flew it well up into the threatening clouds,
and then, touching, the suspended key with his knuckle, received
the electric spark; and a little later he charged a Leyden jar
from the electricity drawn from the clouds with his kite.
In a brief but direct letter, he sent an account of his kite and
his experiment to England:
"Make a small cross of two light strips of cedar," he wrote, "the
arms so long as to reach to the four corners of a large, thin,
silk handkerchief when extended; tie the corners of the
handkerchief to the extremities of the cross so you have the body
of a kite; which being properly accommodated with a tail, loop,
and string, will rise in the air like those made of paper; but
this being of silk is fitter to bear the wind and wet of a
thunder-gust without tearing. To the top of the upright stick of
the cross is to be fixed a very sharp-pointed wire, rising a foot
or more above the wood. To the end of the twine, next the hand,
is to be tied a silk ribbon; where the silk and twine join a key
may be fastened. This kite is to be raised when a thunder-gust
appears to be coming on, and the person who holds the string must
stand within a door or window or under some cover, so that the
silk ribbon may not be wet; and care must be taken that the twine
does not touch the frame of the door or window. As soon as any of
the thunder-clouds come over the kite, the pointed wire will draw
the electric fire from them, and the kite, with all the twine,
will be electrified and the loose filaments will stand out
everywhere and be attracted by the approaching finger, and when
the rain has wet the kite and twine so that it can conduct the
electric fire freely, you will find it stream out plentifully
from the key on the approach of your knuckle, and with this key
the phial may be charged; and from electric fire thus obtained
spirits may be kindled and all other electric experiments
performed which are usually done by the help of a rubbed glass
globe or tube, and thereby the sameness of the electric matter
with that of lightning completely demonstrated."
In experimenting with lightning and Franklin's pointed rods in
Europe, several scientists received severe shocks, in one case
with a fatal result. Professor Richman, of St. Petersburg, while
experimenting during a thunder-storm, with an iron rod which he
had erected on his house, received a shock that killed him
About 1733, as we have seen, Dufay had demonstrated that there
were two apparently different kinds of electricity; one called
VITREOUS because produced by rubbing glass, and the other
RESINOUS because produced by rubbed resinous bodies. Dufay
supposed that these two apparently different electricities could
only be produced by their respective substances; but twenty years
later, John Canton (1715-1772), an Englishman, demonstrated that
under certain conditions both might be produced by rubbing the
same substance. Canton's experiment, made upon a glass tube with
a roughened surface, proved that if the surface of the tube were
rubbed with oiled silk, vitreous or positive electricity was
produced, but if rubbed with flannel, resinous electricity was
produced. He discovered still further that both kinds could be
excited on the same tube simultaneously with a single rubber. To
demonstrate this he used a tube, one-half of which had a
roughened the other a glazed surface. With a single stroke of the
rubber he was able to excite both kinds of electricity on this
tube. He found also that certain substances, such as glass and
amber, were electrified positively when taken out of mercury, and
this led to his important discovery that an amalgam of mercury
and tin, when used on the surface of the rubber, was very
effective in exciting glass.
XV. NATURAL HISTORY TO THE TIME OF LINNAeUS
Modern systematic botany and zoology are usually held to have
their beginnings with Linnaeus. But there were certain precursors
of the famous Swedish naturalist, some of them antedating him by
more than a century, whose work must not be altogether
ignored--such men as Konrad Gesner (1516-1565), Andreas
Caesalpinus (1579-1603), Francisco Redi (1618-1676), Giovanni
Alfonso Borelli (1608-1679), John Ray (1628-1705), Robert Hooke
(1635-1703), John Swammerdam (1637-1680), Marcello Malpighi
(1628-1694), Nehemiah Grew (1628-1711), Joseph Tournefort
(1656-1708), Rudolf Jacob Camerarius (1665-1721), and Stephen
Hales (1677-1761). The last named of these was, to be sure, a
contemporary of Linnaeus himself, but Gesner and Caesalpinus
belong, it will be observed, to so remote an epoch as that of
Reference has been made in an earlier chapter to the microscopic
investigations of Marcello Malpighi, who, as there related, was
the first observer who actually saw blood corpuscles pass through
the capillaries. Another feat of this earliest of great
microscopists was to dissect muscular tissue, and thus become the
father of microscopic anatomy. But Malpighi did not confine his
observations to animal tissues. He dissected plants as well, and
he is almost as fully entitled to be called the father of
vegetable anatomy, though here his honors are shared by the
Englishman Grew. In 1681, while Malpighi's work, Anatomia
plantarum, was on its way to the Royal Society for publication,
Grew's Anatomy of Vegetables was in the hands of the publishers,
making its appearance a few months earlier than the work of the
great Italian. Grew's book was epoch-marking in pointing out the
sex-differences in plants.
Robert Hooke developed the microscope, and took the first steps
towards studying vegetable anatomy, publishing in 1667, among
other results, the discovery of the cellular structure of cork.
Hooke applied the name "cell" for the first time in this
connection. These discoveries of Hooke, Malpighi, and Grew, and
the discovery of the circulation of the blood by William Harvey
shortly before, had called attention to the similarity of animal
and vegetable structures. Hales made a series of investigations
upon animals to determine the force of the blood pressure; and
similarly he made numerous statical experiments to determine the
pressure of the flow of sap in vegetables. His Vegetable Statics,
published in 1727, was the first important work on the subject of
vegetable physiology, and for this reason Hales has been called
the father of this branch of science.
In botany, as well as in zoology, the classifications of Linnaeus
of course supplanted all preceding classifications, for the
obvious reason that they were much more satisfactory; but his
work was a culmination of many similar and more or less
satisfactory attempts of his predecessors. About the year 1670
Dr. Robert Morison (1620-1683), of Aberdeen, published a
classification of plants, his system taking into account the
woody or herbaceous structure, as well as the flowers and fruit.
This classification was supplanted twelve years later by the
classification of Ray, who arranged all known vegetables into
thirty-three classes, the basis of this classification being the
fruit. A few years later Rivinus, a professor of botany in the
University of Leipzig, made still another classification,
determining the distinguishing character chiefly from the flower,
and Camerarius and Tournefort also made elaborate
classifications. On the Continent Tournefort's classification was
the most popular until the time of Linnaeus, his systematic
arrangement including about eight thousand species of plants,
arranged chiefly according to the form of the corolla.
Most of these early workers gave attention to both vegetable and
animal kingdoms. They were called naturalists, and the field of
their investigations was spoken of as "natural history." The
specialization of knowledge had not reached that later stage in
which botanist, zoologist, and physiologist felt their labors to
be sharply divided. Such a division was becoming more and more
necessary as the field of knowledge extended; but it did not
become imperative until long after the time of Linnaeus. That
naturalist himself, as we shall see, was equally distinguished as
botanist and as zoologist. His great task of organizing knowledge
was applied to the entire range of living things.
Carolus Linnaeus was born in the town of Rashult, in Sweden, on
May 13, 1707. As a child he showed great aptitude in learning
botanical names, and remembering facts about various plants as
told him by his father. His eagerness for knowledge did not
extend to the ordinary primary studies, however, and, aside from
the single exception of the study of physiology, he proved
himself an indifferent pupil. His backwardness was a sore trial
to his father, who was desirous that his son should enter the
ministry; but as the young Linnaeus showed no liking for that
calling, and as he had acquitted himself well in his study of
physiology, his father at last decided to allow him to take up
the study of medicine. Here at last was a field more to the
liking of the boy, who soon vied with the best of his
fellow-students for first honors. Meanwhile he kept steadily at
work in his study of natural history, acquiring considerable
knowledge of ornithology, entomology, and botany, and adding
continually to his collection of botanical specimens. In 1729 his
botanical knowledge was brought to the attention of Olaf Rudbeck,
professor of botany in the University of Upsala, by a short paper
on the sexes of plants which Linnaeus had prepared. Rudbeck was
so impressed by some of the ideas expressed in this paper that he
appointed the author as his assistant the following year.
This was the beginning of Linnaes's career as a botanist. The
academic gardens were thus thrown open to him, and he found time
at his disposal for pursuing his studies between lecture hours
and in the evenings. It was at this time that he began the
preparation of his work the Systema naturae, the first of his
great works, containing a comprehensive sketch of the whole field
of natural history. When this work was published, the clearness
of the views expressed and the systematic arrangement of the
various classifications excited great astonishment and
admiration, and placed Linaeus at once in the foremost rank of
naturalists. This work was followed shortly by other
publications, mostly on botanical subjects, in which, among other
things, he worked out in detail his famous "system."
This system is founded on the sexes of plants, and is usually
referred to as an "artificial method" of classification because
it takes into account only a few marked characters of plants,
without uniting them by more general natural affinities. At the
present time it is considered only as a stepping-stone to the
"natural" system; but at the time of its promulgation it was
epoch-marking in its directness and simplicity, and therefore
superiority, over any existing systems.
One of the great reforms effected by Linnaeus was in the matter
of scientific terminology. Technical terms are absolutely
necessary to scientific progress, and particularly so in botany,
where obscurity, ambiguity, or prolixity in descriptions are
fatally misleading. Linnaeus's work contains something like a
thousand terms, whose meanings and uses are carefully explained.
Such an array seems at first glance arbitrary and unnecessary,
but the fact that it has remained in use for something like two
centuries is indisputable evidence of its practicality. The
descriptive language of botany, as employed by Linnaeus, still
stands as a model for all other subjects.
Closely allied to botanical terminology is the subject of
botanical nomenclature. The old method of using a number of Latin
words to describe each different plant is obviously too
cumbersome, and several attempts had been made prior to the time
of Linnaeus to substitute simpler methods. Linnaeus himself made
several unsatisfactory attempts before he finally hit upon his
system of "trivial names," which was developed in his Species
plantarum, and which, with some, minor alterations, remains in
use to this day. The essence of the system is the introduction of
binomial nomenclature--that is to say, the use of two names and
no more to designate any single species of animal or plant. The
principle is quite the same as that according to which in modern
society a man has two names, let us say, John Doe, the one
designating his family, the other being individual. Similarly
each species of animal or plant, according to the Linnaeean
system, received a specific or "trivial" name; while various
species, associated according to their seeming natural affinities
into groups called genera, were given the same generic name. Thus
the generic name given all members of the cat tribe being Felis,
the name Felis leo designates the lion; Felis pardus, the
leopard; Felis domestica, the house cat, and so on. This seems
perfectly simple and natural now, but to understand how great a
reform the binomial nomenclature introduced we have but to
consult the work of Linnaeus's predecessors. A single
illustration will suffice. There is, for example, a kind of
grass, in referring to which the naturalist anterior to Linnaeus,
if he would be absolutely unambiguous, was obliged to use the
following descriptive formula: Gramen Xerampelino, Miliacea,
praetenuis ramosaque sparsa panicula, sive Xerampelino congener,
arvense, aestivum; gramen minutissimo semine. Linnaeus gave to
this plant the name Poa bulbosa--a name that sufficed, according
to the new system, to distinguish this from every other species
of vegetable. It does not require any special knowledge to
appreciate the advantage of such a simplification.
While visiting Paris in 1738 Linnaeus met and botanized with the
two botanists whose "natural method" of classification was later
to supplant his own "artificial system." These were Bernard and
Antoine Laurent de Jussieu. The efforts of these two scientists
were directed towards obtaining a system which should aim at
clearness, simplicity, and precision, and at the same time be
governed by the natural affinities of plants. The natural system,
as finally propounded by them, is based on the number of
cotyledons, the structure of the seed, and the insertion of the
stamens. Succeeding writers on botany have made various
modifications of this system, but nevertheless it stands as the
foundation-stone of modern botanical classification.
SCIENCE IN THE DARK AGE
 (p. 4). James Harvey Robinson, An Introduction to the History
of Western Europe, New York, 1898, p. 330.
 (p. 6). Henry Smith Williams, A Prefatory Characterization of
The History of Italy, in vol. IX. of The Historians' History of
the World, 25 vols., London and New York, 1904.
MEDIAeVAL SCIENCE IN THE WEST
 (p. 47). Etigene Muntz, Leonardo do Vinci, Artist, Thinker,
and Man of Science, 2 vols., New York, 1892. Vol. II., p. 73.
THE NEW COSMOLOGY--COPERNICUS TO KEPLER AND GALILEO
 (p. 62). Copernicus, uber die Kreisbewegungen der Welfkorper,
trans. from Dannemann's Geschichle du Naturwissenschaften, 2
vols., Leipzig, 1896.
 (p. 90). Galileo, Dialogo dei due Massimi Systemi del Mondo,
trans. from Dannemann, op. cit.
GALILEO AND THE NEW PHYSICS  (p. 101). Rothmann, History of
Astronomy (in the Library of Useful Knowledge), London, 1834.
 (p. 102). William Whewell, History of the Inductive Sciences,
3 Vols, London, 1847-Vol. II., p. 48.
 (p. 111). The Lives of Eminent Persons, by Biot, Jardine,
Bethune, etc., London, 1833.
 (p. 113). William Gilbert, De Magnete, translated by P.
Fleury Motteley, London, 1893. In the biographical memoir, p.
 (p. 114). Gilbert, op. cit., p. x1vii.
 (p. 114). Gilbert, op. cit., p. 24.
TWO PSEUDO-SCIENCES--ALCHEMY AND ASTROLOGY
 (p. 125). Exodus xxxii, 20.
 (p. 126). Charles Mackay, Popular Delusions, 3 vols., London,
1850. Vol. II., p. 280.
 (p. 140). Mackay, op. cit., Vol. 11., p. 289.
 (P. 145). John B. Schmalz, Astrology Vindicated, New York,
 (p. 146). William Lilly, The Starry Messenger, London, 1645,
 (p. 149). Lilly, op. cit., p. 70.
 (p. 152). George Wharton, An Astrological jugement upon His
Majesty's Present March begun from Oxford, May 7, 1645, pp. 7-10.
 (p. 154). C. W. Roback, The Mysteries of Astrology, Boston,
1854, p. 29.
FROM PARACELSUS TO HARVEY
 (p. 159). A. E. Waite, The Hermetic and Alchemical Writings
of Paracelsus, 2 vols., London, 1894. Vol. I., p. 21.
 (p. 167). E. T. Withington, Medical History from the Earliest
Times, London, 1894, p. 278.
 (p. 173). John Dalton, Doctrines of the Circulation,
Philadelphia, 1884, p. 179.
 (p. 174). William Harvey, De Motu Cordis et Sanguinis,
London, 1803, chap. X.
 (p. 178). The Works of William Harvey, translated by Robert
Willis, London, 1847, p. 56.
MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES
 (p. 189). Hermann Baas, History of Medicine, translated by H.
E. Henderson, New York, 1894, p. 504.
 (p. 189). E. T. Withington, Medical History from the Earliest
Times, London, 1894, p. 320.
PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF LEARNING
 (p. 193). George L. Craik, Bacon and His Writings and
Philosophy, 2 vols., London, 1846. Vol. II., p. 121.
 (p. 193). From Huxley's address On Descartes's Discourse
Touching the Method of Using One's Reason Rightly and of Seeking
 (p. 195). Rene Descartes, Traite de l'Homme (Cousins's
edition. in ii vols.), Paris, 1824. Vol, VI., p. 347.
THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE
 (p. 205). See The Phlogiston Theory, Vol, IV.
 (p. 205). Robert Boyle, Philosophical Works, 3 vols., London,
1738. Vol. III., p. 41.
 (p. 206). Ibid., Vol. III., p. 47.
 (p. 206). Ibid., Vol. II., p. 92.
 (p. 207). Ibid., Vol. II., p. 2.
 (p. 209). Ibid., Vol. I., p. 8.
 (p. 209). Ibid., vol. III., p. 508.
 (p. 210). Ibid., Vol. III.) p. 361.
 (p. 213). Otto von Guericke, in the Philosophical
Transactions of the Royal Society of London, No. 88, for 1672, p.
 (p. 222). Von Guericke, Phil. Trans. for 1669, Vol I., pp.
NEWTON AND THE COMPOSITION OF LIGHT
 (p. 233). Phil. Trans. of Royal Soc. of London, No. 80, 1672,
pp. 3076-3079.  (p 234). Ibid., pp. 3084, 3085.
 (p. 235). Voltaire, Letters Concerning the English Nation,
NEWTON AND THE LAW OF GRAVITATION
 (p. 242). Sir Isaac Newton, Principia, translated by Andrew
Motte, New York, 1848, pp. 391, 392.
 (p. 250). Newton op. cit., pp. 506, 507.
PROGRESS IN ELECTRICITY FROM GILBERT AND VON GUERICKE TO FRANKLIN
 (p. 274). A letter from M. Dufay, F.R.S. and of the Royal
Academy of Sciences at Paris, etc., in the Phil. Trans. of the
Royal Soc., vol. XXXVIII., pp. 258-265.
 (p. 282). Dean von Kleist, in the Danzick Memoirs, Vol. I.,
p. 407. From Joseph Priestley's History of Electricity, London,
1775, pp. 83, 84.
 (p. 288). Benjamin Franklin, New Experiments and Observations
on Electricity, London, 1760, pp. 107, 108.
 (p. 291). Franklin, op. cit., pp. 62, 63.
 (p. 295). Franklin, op. cit., pp. 107, 108.
[For notes and bibliography to vol. II. see vol. V.]