Full Text Archive logoFull Text Archive — Free Classic E-books

Scientific American Supplement, No. 601, July 9, 1887 by Various

Part 2 out of 2

Adobe PDF icon
Download this document as a .pdf
File size: 0.2 MB
What's this? light bulb idea Many people prefer to read off-line or to print out text and read from the real printed page. Others want to carry documents around with them on their mobile phones and read while they are on the move. We have created .pdf files of all out documents to accommodate all these groups of people. We recommend that you download .pdfs onto your mobile phone when it is connected to a WiFi connection for reading off-line.

malm stocks, which are superior in color and texture, are made, and are
used for facing bricks and for cutting; and what are called paviors,
which are dark and strong bricks, are also made. The London stock is
erroneously, but usually, described as gray. It is really of a pie crust
yellow of various tones. Sometimes it is the same color when cut, but
the hardest stocks are of a dark, dirty purple or brown, or sometimes
nearly black inside. A stock brick is rarely quite square or quite true;
its surface is often disfigured by black specks and small pits, and a
stack of them often looks uninviting; yet a skillful bricklayer, by
throwing out the worst, by placing those of bad colors or much out of
shape in the heart of the wall, and by bringing to the front the best
end or side of those bricks which form part of the face, can always make
the bricks in his work look far better than in the stack. Another
important group is the group of Suffolk and Norfolk bricks, red and
white. These are very largely employed as facing bricks and for arches
and cut mouldings.

Moulded bricks are also to a large extent made of the same material.
These bricks are brought to London in large quantities. They have a
sanded face, are mostly square, true, and of uniform color, but they are
usually porous, soft, and absorbent. Still, they are in great demand as
facing bricks, and the moulded bricks enable the architect to produce
many architectural effects at a moderate outlay. These fields furnish
many sorts of bricks, which are called rubbers, and which are employed
(as malm stocks also are) for arches of the more elaborate sort, where
each brick is cut to its shape and rubbed true, and for mouldings, and
even sometimes for carving.

Mouldings that are formed by cutting the bricks can be got more
perfectly true than when moulded bricks are used; but the expense is
greater, and when it is done the material is less durable, for the
softer sorts of brick are naturally used for cutting, and the moulded
face is less sound than the original burnt face of any brick. Red bricks
are to some extent made in fields within easy reach of London; but the
best come from some distance. Red Suffolk bricks have been alluded to.
There is a considerable importation of red Fareham bricks, brought all
the way from the vicinity of Portsmouth; these are good both in quality
and color. Good red bricks are also now made at Ascot, and are being
used to a considerable extent in the metropolis. A strawberry-colored
brick from Luton has been extensively used at Hampstead. It is hard, and
of a color which contrasts well with stone, but not very pleasing used
alone. Glazed bricks of all colors are obtainable. They are usually very
hard and square, and the use of them where an impervious glazed face is
required, as, for example, in a good stable, is better than the
employment of glazed tiles, in the employment of which there is always a
possibility of part of the lining becoming loose or falling off. There
is a difficulty in obtaining a large quantity (of some colors, at least)
exactly uniform in tint. Bricks with a very hard face, but not glazed,
are obtainable. What is called a washing brick is now made in various
colors, adapted for the lining of interiors, and there are hard bricks
of a very pale straw color, known as Beart's patent bricks, made, I
believe, of gault clay, which were some years ago bought up by the Great
Northern Railway in large numbers. These bricks have the peculiarity of
being pierced with holes about 1/2 in. in diameter, passing quite through
the brick, and they are extremely hard, partly because these holes
permit the hot air and smoke in the kiln to approach very near to the
interior of the brick. I am of opinion that the glazed or dull qualities
of hard bricks might with great advantage be often introduced into
London streets. What we want is something that will wash. The rough
surface of stocks or Suffolk facing bricks catches the black in the
London atmosphere and gradually gets dark and dull. A perfectly hard
face is washed clean by every shower. A good many years ago I built a
warehouse with stock bricks, and formed the arches, strings, etc., of
bricks with a very hard face, and, as I expected, the effect of time has
been to make these features stand out far better than when they were
fresh; in fact, the only question is whether they have not now become
too conspicuous. To return to the bricks in the London market: we have
firebricks made of fireclay, and almost vitrified and capable of
standing intense heat. These are used for lining furnaces, ovens, flues,

Then we have almost, if not quite, as refractory a material in
Staffordshire blue bricks, used--in various forms--for paving channels,
jambs of archways, etc. There are also small bricks called clinkers,
chiefly used for stable paving. Dutch clinkers, formerly imported
largely from Holland, were small, rough bricks, laid on edge, and
affording a good foothold for the horse. Adamantine clinkers, made of
gault clay, are much used; they must have chamfered edges, otherwise
they make too smooth a floor for a stable. Many other varieties are
obtainable in London, and are more or less used, but these are the most
prominent. In many parts of England special varieties of brick are to be
found, and every here and there one falls upon a good brickmaker who is
able to produce good moulded or embossed or ornamental bricks, such as
those which have been supplied to me years ago by Mr. Gunton, and more
recently by Mr. Brown, both of Norwich, or by Mr. Cooper, of Maidenhead.

It is of importance to those whose business it is to look after or
engage in building operations, that they should early learn what to look
out for in each material. Of course, a man only becomes a judge of
bricks, or timber, or stone by experience; but he is far better able to
take the benefit of experience when it comes to him if he knows from the
first to what points to direct attention. Wherefore I make no apology
for trying to put before you the points of a good brick, and in doing so
I shall partly quote from a memorandum published now a good many years
ago by the Manchester Society of Architects.

A good brick is uniform in size; standard, 9 by 41/2 by 21/2 in.; weight
about 7 lb. each = 110 lb. per foot cube; is rectangular, true faced,
but only one end and one side need be smooth; has no print sinking on
either face, but a hollow on one or both beds. When saturated with
water, a brick should not absorb more than 20 per cent, of its own
weight of water, should absorb it reluctantly, and part with it freely
at ordinary temperatures. It should be uniformly burnt, should be sound,
free from cracks, flaws, stones, lumps of any kind, but especially lumps
of lime, should be of a good color for its sort (whether red, yellow, or
white), should have a metallic clang when two bricks are struck
together; when broken should be sound right through, should be tough and
pasty in texture, not granular, and should require repeated blows to
break it, rather than one hard blow (such bricks will withstand cartage
and handling best). So much for bricks. To make brickwork, however,
another ingredient is required--namely, mortar or cement.

All mortars and, in fact, all the cementing materials used (except
bituminous ones) in bricklaying have lime as their base, and depend upon
the setting quality of quicklime, which has to be mixed with sand or
some suitable substitute for it, to make mortars. Limes and cements are
far too wide a subject to be dealt with as part of an evening's lecture
on another topic, and no doubt they will hereafter form the subject of a
lecture or lectures. To-night I propose only to remind you that there
are such substances as these, and that they possess certain qualities
and are obtainable and available for the bricklayer's purposes, without
attempting an investigation into the chemistry of cements, or their
manufacture, etc. Ordinarily, brickwork may be divided into brickwork in
mortar and in cement; but there are many qualities of mortar and several
sorts of cement. Mortar made with what are called fat or rich
limes--that is to say, nearly pure lime, such as is got by calcining
marble or pure chalk--sets slowly, with difficulty, and is rarely
tenacious. Burnt clay or brick reduced to powder improves the setting of
such lime, especially if the two materials be calcined together; so will
an admixture of cement. Mortar made with what is known as slightly
hydraulic lime, that is to say, lime containing a small proportion of
clay, such as the gray stone lime of Dorking, Merstham, and that
neighborhood, sets well, and is tenacious and strong. Mortar made with
hydraulic lime, that is to say, lime with a considerable admixture of
clay, such as the lias lime, sets under water or in contact with wet
earth. It is best to use this lime ground to powder, and not to mix so
much sand with it as is used with stone lime. A sort of mortar called
selenitic mortar, the invention of the late General Scott, has been made
use of in many of the buildings of the School Board for London, and was
first employed on a large scale in the erection of the Albert Hall. The
peculiarity consists in the addition of a small dose of plaster of Paris
(sulphate of lime) very carefully introduced and intimately mixed. The
result is that the mortar so made sets rapidly, and is very hard.

It is claimed that a larger proportion of sand can be used with
selenitic lime than with ordinary, thus counterbalancing the extra
expense occasioned by royalty under the patent and special care in
mixing. When a limestone contains 20 to 40 per cent, of clay, it becomes
what is called a cement, and its behavior is different from that of
limestones with less clay. Ordinary limestones are, as you know,
calcined in a kiln. The material which comes from the kiln is called
quicklime, and, on being dosed with water, it slakes, and crumbles to
powder, and in the state of slaked lime is mixed up with mortar. Cement
stones are also calcined; but the resulting material will not fall to
pieces or slake under water. It must be ground very fine, and when
moistened sets rapidly, and as well under water as in air, and becomes
very hard and is very tenacious. Brickwork in mortar will always settle
and compress to some extent. Not so brickwork in cement, which
occasionally expands, but is never to be compressed. This quality and
the rapid setting, tenacity, and strength of brickwork in cement make it
a most valuable material to use in those buildings or parts of a
building where great steadiness and strength are wanted, and in sewage
and dock work, where there is water to contend with. A good many cements
made from natural stones used to be employed, such as Medina, Harwich,
Atkinson's, or Roman cement. The last named is the only one which is now
much employed, except locally. It has the quality of setting with
exceptional rapidity, and is on that account sometimes the best material
to employ; but for almost every purpose the artificial compound known as
Portland cement is preferable.

Portland cement is made largely near Rochester. Its materials are simple
and cheap. They may, without much departure from the truth, be said to
be Thames mud and chalk; but the process of manufacture requires care
and thoroughness. The article supplied, when of the best quality, has
great strength, and is quick setting, and is far better than what was
manufactured from stones in which the ingredients existed in a state of
nature. In England we slake our lime and make use of it while it is
fresh; but it may interest you to know that the custom in Italy and
parts of France is different. There it is customary to slake the lime
long before it is wanted, and to deposit it in a pit and cover it up
with earth. In this condition it is left for months--I believe in Italy
for a year--and when taken out it is stiff, but still a pasty substance.
It is beaten, and more water added, and it is then made into mortar with
sand. It is claimed for mortar made in this way that is exceptionally

Now that we have considered bricks and partly considered mortar, it
remains to pay some attention to brickwork. The simplest and most
familiar work for a bricklayer to do is to build a wall. In doing this
his object should be to make it as stout as possible for the thickness,
and this stoutness can only be obtained by interlacing the bricks. If
they were simply laid on the top of each other, the wall would be no
more than a row of disconnected piles of bricks liable to tumble down.
When the whole is so adjusted that throughout the entire wall the joints
in one course shall rest on solid bricks and shall be covered by solid
bricks again--in short, when the whole shall break joint--then this wall
is said to be properly bonded, and has as much stability given to it as
it can possibly possess. There are two systems of bonding in use in
London, know as English bond and Flemish bond. English bond is the
method which we find followed in ancient brickwork in this country.

In this system a course of bricks is laid across the wall, showing their
heads at the surface, hence called "headers," and next above comes a
course of bricks stretching lengthways at the wall, called stretchers,
and so on alternately. With the Dutch fashions came in Flemish bond, in
which, in each course, a header and a stretcher alternate. In either
case, at the corners, a quarter-brick called a closer has to be used in
each alternate course to complete the breaking joint. There is not much
to choose between these methods where the walls are only one brick
thick. But where they are thicker the English has a decided advantage,
for in walls built in Flemish bond of one and a half brick thickness or
more there must be a few broken bricks, or bats, and there is a strong
temptation to make use of many. If this takes place, the wall is

Many of the failures of brickwork in London houses arise from the
external walls, where they are 11/2 bricks thick, being virtually in two
skins; the inner 9 in. does the whole of the work of supporting floors
and roof, and when it begins to fail, the outer face bulges off like a
large blister. I have known cases where this had occurred, and where
there was no header brick for yards, so that one could pass a 5 ft. rod
into the space between the two skins and turn it about. This is rather
less easy to accomplish with English bond, and there are other
advantages in the use of that bond which make it decidedly preferable,
and it is now coming back into very general use. There are some odd
varieties of bond, such as garden bond and chimney bond. But of these I
only wish to draw your attention to what is called cross bond. The name
is not quite a happy one. Diagonal bond is hardly better. The thing
itself is to be often met with on the Continent, and it is almost
unknown here. But it would be worth introducing, as the effect of it is
very good.

French cross bond, otherwise diagonal bond _(liaison en croix)_, is
English bond, but with the peculiarity that in every fourth course one
header is made use of in the stretcher course at the quoin. The result
is that the stretchers break joint with each other, and all the joints
range themselves in diagonal lines, and if in any part of the work
headers of a different brick are introduced, the appearance of a cross
is at once brought out; and even without this the diagonal arrangement
of joints is very perceptible and pleasing.

Besides wall building, the bricklayer has many other works to perform.
He has to form fireplaces, flues, chimneys, and the flat trimmer arches
which support the hearth, and has to set the stove, kitchen range,
copper, etc., in a proper manner. He has to form various ornamental
features and much else, some of which we shall have an opportunity of
noticing rather later. The strangest business, however, which is
intrusted to the bricklayer is building downward--by the method known as
underpinning--so that if a foundation has failed, a sounder one at a
greater depth may be reached; or if a basement is required under an
existing building which has none, the space may be excavated and the new
walls built so as to maintain the old.

This work has to be done with great caution, and bit by bit, and is
usually left to experienced hands. The mode in which the mortar joints
of a brick wall are finished where they show on the external or internal
face is a matter worth a moment's attention. It is important that the
joints of the work shall be so finished as to keep out wet and to be as
durable as possible, and it is desirable that they should improve, or at
any rate not disfigure, the appearance of the work.

The method which architects strongly advocate is that the joints shall
be struck as the work proceeds--that is, that very shortly after a brick
is laid, and while the mortar is yet soft, the bricklayer shall draw his
trowel, or a tool made for the purpose, across it, to give it a smooth
and a sloping surface. This is best when the joint is what is called a
weather joint--i.e., one in which the joint slopes outward. Sloping it
inward is not good, as it lets in wet; finishing it with a hollow on the
face is often practiced, and is not bad. Bricklayers, however, most of
them prefer that the mortar joints should be raked out and pointed--that
is to say, an inch or an inch and a half of the mortar next the outer
face be scratched out and replaced with fresh mortar, and finished to a

In cases where the brickwork is exposed to frost, this proceeding cannot
be avoided, because the frost damages the external mortar of the joints.
But the bricklayers prefer it at all seasons of the year, partly because
brickwork is more quickly done if joints are not struck at the time;
partly because they can, if they like, wash the whole surface of the
work with ocher, or other color, to improve the tint; and partly
because, whether the washing is done or not, it smartens up the
appearance of the work. The misfortune is that this pointing, instead of
being the edge of the same mortar that goes right through, is only the
edge of a narrow strip, and does not hold on to the old undisturbed
mortar, and so is far less sound, and far more liable to decay. There is
a system of improving the appearance of old, decayed work by raking out
and filling up the joint, and then making a narrow mortar joint in the
middle of this filling in, and projecting from the face. This is called
tuck pointing. It is very specious, but it is not sound work.

Brick arches are constantly being turned, and of many sorts. An arch
consists of a series of wedge shaped blocks, known as voussoirs,
arranged in a curve, and so locking one another together that unless the
abutments from which the arch springs give way, it will not only carry
itself, but sustain a heavy load. It is a constant practice to cut
bricks to this shape and build them into an arch, and these are
sometimes cut and rubbed; sometimes, when the work is rougher, they are
axed. But in order to save the labor of cutting, arches are sometimes
turned with the bricks left square, and the joints wedge shaped. In this
case the rings should be only half a brick each, so that the wedge need
not be so very much wider at back than at face, and they are set in
cement, as that material adheres so closely and sets so hard. Arches of
two or more half-brick rings in cement are good construction, and are
also used for culvert work.

A less satisfactory sort of arch is what is called the flat arch. Here,
instead of being cambered as it ought to be, the soffit is straight; but
the brickwork being deep, there is room enough for a true arch that does
the work, and for useless material to hang from it. These arches are
generally rubbed or axed, and are very common at the openings of
ordinary windows. But no one who has studied construction can look at
them without a kind of wish for at least a slight rise, were it only two
inches. Sometimes when these straight arches are to be plastered over
they are constructed in a very clumsy manner, which is anything but
sound, and from time to time they give way. The weight of brickwork, of
course, varies with the weight of the individual bricks. But stock
brickwork in mortar weighs just about one hundred weight per cubic foot,
or 20 cubic feet to the ton. In cement it is heavier, about 120 lb. to
the cubic foot.

The strength of brickwork depends of course on the strength of the
weakest material--i.e., the mortar--though when it is in cement the
strength of brickwork to withstand a weight probably approaches that of
the individual bricks. Some experiments quoted in Rivington's Notes give
the following as the crushing weight per foot--that is to say, weight at
which crushing began--of piers having a height of less than twelve times
their diameter:

Tons per
Best stocks, set in Portland cement and
sand 1 to 1, and three months old. 40
Ordinary good stocks, three months old. 30
Hard stocks, Roman cement and sand 1 to 1,
three months old. 28
Hard stocks, lias lime, and sand 1 to 2,
and six months old. 24
Hard stocks, gray chalk lime, and sand,
six months old. 12

The rule given in popular handbook, that brickwork in mortar should not
have to carry more than three tons per superficial foot, and in cement
more than five tons, is probably sound, as in no building ought the load
to approach the crushing point, and, indeed, there are many sorts of
foundations on which such a load as five tons per foot would be too
great to be advisable.

It is a rather interesting inquiry, whenever we are dealing with a
building material, if we ask what can we best do with it, and for what
is it ill fitted. The purposes for which brick can be best used depend,
of course, upon its qualities. Speaking generally, such purposes are
very numerous and very various, especially the utilitarian purposes,
though rich and varied ornamental work can also be executed in

Perhaps the most remarkable quality of brickwork is that it can be
thrown into almost any shape. It is in this respect almost like a
plastic material, and this peculiarity it owes chiefly to the very small
size of each brick as compared with the large masses of the brickwork of
most buildings. Stone is far less easily dealt with than brick in this
respect. Think for a moment of the great variety of walls, footings,
piers, pilasters, openings, recesses, flues, chimney breasts, chimney
shafts, vaults, arches, domes, fireproof floors, corbels, strings,
cappings, panels, cornices, plinths, and other features met with in
constant use, and all formed by the bricklayer with little trouble out
of the one material--brickwork! A little consideration will convince you
that if the same material furnishes all these, it must be very plastic.
As a limitation we ought to note that this almost plastic material
cannot be suddenly and violently dealt with--that is to say, with the
exception of some sorts of arches, you cannot form any abrupt or
startling feature in brickwork, and you are especially limited as to

If you wish to throw out any bold projection, you may support it on a
long and sloping corbel of brickwork. But if there is not room for that,
you must call in some other material, and form the actual support in
stone, or terra cotta, or iron, and when you have gained your
projection, you may then go on in brickwork if you like.

Brick cornices should be steep, but cannot be bold, and so with other
ornamental and structural features. A noteworthy property of brickwork,
and one of immense value, is that it is thoroughly fireproof; in fact,
almost the only perfectly fireproof material. There is an interesting
account of the great fire of London by one of the eye witnesses, and
among the striking phenomena of that awful time he notes that the few
brick buildings which existed were the only ones able to withstand the
raging fire when it reached them.

In our own day a striking proof of the same thing was given in the great
fire in Tooley street, when Braidwood lost his life. I witnessed that
conflagration for a time from London Bridge, and its fury was something
not to be described. There were vaults under some of the warehouses
stored with inflammable materials, the contents of which caught fire and
burnt for a fortnight, defying all attempts to put them out. Yet these
very vaults, though they were blazing furnaces for all that time, were
not materially injured. When the warehouses came to be reinstated, it
was only found necessary to repair and repoint them a little, and they
were retained in use. The fact is that the bricks have been calcined
already, so has the lime in the mortar, and the sand is not affected by
heat, so there is nothing in brickwork to burn. Against each of these
good qualities, however, we may set a corresponding defect.

If brickwork is easily thrown into any shape, it is also easily thrown
out of shape. It has little coherence or stability, less than masonry
and very considerably less than timber. If any unequal settlement in the
foundation of a brick building occurs, those long zigzag cracks with
which we in London are only too familiar set themselves up at once; and
if any undue load, or any variation in load, exists, the brickwork
begins to bulge. Any serious shock may cause a building of ordinary
brickwork to collapse altogether, and from time to time a formidable
accident occurs owing to this cause. The fact is, the bricks are each so
small compared to the mass of the work, and the tenacity or hold upon
them of even fairly good lime mortar is so comparatively slight, that
there is really but little grip of one put upon another.

Persons who have to design and construct brick buildings should never
forget that they have to be handled with caution, and are really very
ticklish and unstable. One or two of the methods of overcoming this to
some extent may be mentioned. The first is the introduction of what is
called bond. At the end of the last century it was usual to build in, at
every few feet in height, bond timbers, which were embedded in the heart
of the walls. If these had always remained indestructible, they would no
doubt have served their purpose to some extent. Unfortunately, timber
both rots and burns, and this bond timber has brought down many a wall
owing to its being destroyed by fire, and has in other cases decayed
away, and caused cracks, settlements, and failures.

The more modern method of introducing a strong horizontal tie is to
build into the wall a group of bands of thin iron, such as some sorts of
barrels are hooped with--hence called hoop iron. The courses of bricks
where this occurs must be laid in cement, because iron in contact with
cement does not perish as it does in contact with mortar.

If in every story of a building four or five courses are thus laid and
fortified, a great deal of strength is given to the structure. Another
method, which has rather fallen into disuse, is grouting. This is
pouring liquid mortar, about the consistency of gruel, upon the work at
about every fourth course. The result is to fill up all interstices and
cavities, and to delay the drying of the mortar, and brickwork so
treated sets extremely hard. I have seen a wall that had been so treated
cut into, and it was quite as easy to cut the bricks (sound ones though
they were) as the mortar joints.

Grouting is objected to because it interferes with the good look of the
work, as it is very difficult to prevent streaks of it from running down
the face, and it is apt to delay the work. But it is a valuable means of
obtaining strong brickwork. Another and a more popular method is to
build the work in cement, now usually Portland cement. This, of course,
makes very strong, sound work, and does not involve any delay or dirt
like grouting, or the introduction of any fresh material like hoop iron.
But it, of course, adds to the expense of the work considerably, as
cement is much more costly than lime. I ought to add that the advocates
of Scott's selenitic mortar claim that it not only sets quickly and
hard, but that it is extremely tenacious, and consequently makes a much
more robust wall than ordinary mortar. I dare say this is true; but I
have not happened to see such a wall cut into, and this is the best test
of solidity.

The second deficiency in brickwork which I am bound to notice is that,
though it is very fireproof, it is far from being waterproof. In an
exposed situation rain will drive completely through a tolerably stout
brick wall. If water be allowed to drop or fall against it, the wall
will become saturated like a sponge. If the foot of a wall becomes wet,
or if the earth resting against the lower parts of it be moist, water
will, if not checked, rise to a great height in it, and if the upper
part of the wall be wet, the water will sink downward. With most sorts
of brick the outer face absorbs moisture whenever the weather is moist;
and in time the action of the rain, and the subsequent action of frost
upon the moisture so taken up, destroys the mortar in the joints, which
are to be seen perfectly open, as if they had been raked out, in old
brickwork, and in some cases (happily not in many) the action of weather
destroys the bricks themselves, the face decaying away, and the brick
becoming soft.

Against this serious defect in our staple building material a series of
precautions have been devised. Damp rising from the foot of the wall, or
from earth lying round its base, is combated by a damp course--a bed of
some impervious material going through the wall. Damp earth may be kept
off by surrounding the walls with an open area or a closed one--usually
termed a dry area. Damp against the face of the walls may be partly
combated by a careful selection of a non-absorbent brick with a hard
face and by struck joints. But it is most effectually kept at bay by the
expedient of building the wall hollow; that is to say, making the
external wall of the house to consist of two perfectly distinct walls,
standing about 2 in. apart, and held together by ties of earthenware or
iron. The result is that the moisture blowing through the outer skin
does not pass the cavity, but trickles down on the inner face of the
outer wall, while the inner wall remains dry. The ties are constructed
of shapes to prevent their conducting water themselves from without to
the inner wall. In addition to this, a series of slates forming an
intermediate protection is sometimes introduced, and forms an additional
and most valuable screen against weather. Sometimes, the two skins of
the wall are closer together--say 3/4 in.--and the space is filled with a
bituminous material.

A substance of a bituminous nature, called hygeian rock, has been of
late years introduced, and is being extensively used for this purpose;
it is melted and poured into the open space hot, and quickly hardens.
The use of such a material is open to the objection that no air can pass
through it. The rooms of our houses are receiving air constantly through
the walls, and much of the constant current up our chimneys is supplied,
to our great advantage, in this very imperceptible manner. The house
breathes, so to speak, through the pores of its brickwork. When this is
rendered impossible, it seems clear that fiercer draughts will enter
through the chinks and crevices, and that there will be a greater demand
upon flues not in use, occasioning down draught in the chimneys.

Another mode of keeping out weather is to cement the face of the
brickwork. But this hides up the work, and so tends to promote bad work,
besides being often very unsightly.

Among other peculiarities of brickwork are the facilities for
introducing different colors and different textures of surface which it
presents, the ease with which openings and arches can be formed in it,
the possibility of executing ornament and even carving, and the ease
with which brickwork will combine with other building materials. It
cannot be well made use of for columns, though it may readily enough be
turned into piers or pilasters. It cannot, generally speaking, with
advantage be made use of for any large domes, though the inner dome of
St. Paul's and the intermediate cone are of brick, and stand well. But
it is an excellent material for vaulting arcades and all purposes
involving the turning of arches.

Brickwork must be said to be durable, but it requires care. If not of
the best, brickwork within the reach of the constant vibration caused by
the traffic on a railway seems to be in danger of being shaken to
pieces, judging from one or two instances that have come under my own
observation. The mortar, and even in some cases the bricks themselves,
will rapidly deteriorate if moisture be allowed to get into the heart of
a brick wall, and in exposed situations this is very apt to happen. Care
should always be taken to keep the pointing of external brickwork in
good order, and to maintain all copings and other projections intended
to bar the access of water coming down from above, and to stop the
overflowing of gutters and stack pipes, which soon soaks the wall
through and through.

Of course, if there is a failure of foundations, brickwork, as was
pointed out earlier, becomes affected at once. But if these be good, and
the materials used be sound ones, and if the other precautions just
recommended be taken, it will last strong and sturdy for an immense
length of time. In some cases, as for example in the Roman ruins, it has
stood for 1,500 years under every possible exposure and neglect, and
still shows something of a sturdy existence after all, though sadly
mutilated. If we now return to the question, What can be well done in
brickwork? no better answer can be given than to point to what has been
and is being done, especially in London and within our own reach and

Great engineering works, such as railway viaducts, the lining of railway
tunnels, the piers and even the arches of bridges, sewage works, dock
and wharf walls, furnace chimneys, and other works of this sort are
chiefly done in brickwork. And notwithstanding that iron is far more
used by the engineer for some purposes and concrete for others now than
formerly, still there is a great field for brickwork. The late Mr.
Brunel, who was fond of pushing size to extremes, tried how wide a span
he could arch over with brickwork. And I believe the bridge which
carries the G.W.R. over the Thames at Maidenhead has the widest arch he
or any other engineer has successfully erected in brick. This arch has,
it is stated, a span of 128 ft. It is segmental, the radius being 169
ft., and the rise from springing to crown 24 ft., and the depth of the
arch 5 ft. 3 in. Nowadays, of course, no one would dream of anything but
an iron girder bridge in such a position. Mr. Brunel's father, when he
constructed the Thames Tunnel, lined it with brickwork foot by foot as
he went on, and that lining sustained the heavy weight of the bed of the
river and the river itself.

If you leave London by either of the southern lines, all of which are at
a high level, you go for miles on viaducts consisting of brick arches
carried on brick walls. If you leave by the northern lines, you plunge
into tunnel after tunnel lined with brickwork, and kept secure by such
lining. Mile after mile of London streets, and those in the suburbs,
present to the eye little but brick buildings; dwelling houses, shops,
warehouses, succeed one another, all in brickwork, and even when the eye
seems to catch a change, it is more apparent than real.

The white mansions of Tyburnia, Belgravia, South Kensington, and the
neat villas of the suburbs are only brickwork, with a thin coat of
stucco, which serves the purpose of concealing the real structure--often
only too much in need of concealment--with a material supposed to be a
little more sightly, and certainly capable of keeping the weather out
rather more effectually than common brickwork would.

More than this, such fine structures, apparently built entirely of
stone, as are being put up for commercial purposes in the streets of the
city, and for public purposes throughout London, are all of them nothing
more than brick fabrics with a facing of masonry. Examine one of them in
progress, and you will find the foundations and vaults of brickwork, and
not only the interior walls, but the main part of the front wall,
executed in brickwork, and the stone only skin deep. There are, however,
two or three ways of making use of brickwork without covering it up, and
of gaining good architectural effects thereby, and to these I beg now to
direct your attention.

The architect who desires to make an effective brick building, which
shall honestly proclaim to all the world that it is of brick, may do
this, and, if he will, may do it successfully, by employing brickwork
and no other material, but making the best use of the opportunities
which it affords, or he may erect his building of brickwork and stone
combined, or of brickwork and terra cotta. Mr. Robson, till lately the
architect to the School Board for London, has the merit of having put
down in every part of the metropolis a series of well contrived and well
designed buildings, the exterior of which almost without exception
consists of brickwork only.

If you examine one of his school-houses, you will see that the walls are
of ordinary stock brickwork, but usually brightened up by a little red
brick at each angle, and surmounted by well contrasted gables and with
lofty, well designed chimneys, rising from the tiled roof. The window
openings and doorways are marked by brickwork, usually also red, and
sometimes moulded, and though I personally must differ from the taste
which selected some of the forms employed (they are those in use in this
country in the 17th and the last centuries), I cordially recognize that
with very simple and inexpensive means exceedingly good, appropriate,
and effective buildings have been designed.

Among examples of architecture wholly, or almost wholly, executed in red
brick, I cannot pass over a building built many years ago, little known
on account of its obscure situation, but a gem in its way. I allude to
the schools designed by Mr. Wilde, and built in Castle street, Endell

Of buildings where a small amount of stone is introduced into brickwork
we have a good many fine specimens in London. One of the best--probably
the best--is the library in Lincoln's Inn Fields. This is a large and
picturesque pile, built under Mr. Hardwick, as architect, in red brick,
with patterns in the blank parts of the walls done in black brick. It
has splendid moulded brick chimneys, and the mullions of the windows,
the copings, the entrances, and some other architectural features done
in stone. The building is a good reproduction of the style of building
in Tudor times, when, as has been already mentioned, brickwork was taken
into favor.

Another building of the same class, but not so good, is the older part
of the Consumption Hospital, at Brompton. Brickwork, with a little
stone, has been very successfully employed as the material for churches,
and in many such cases the interior is of unplastered brickwork. Such
churches often attain, when designed by skillful hands, great dignity
and breadth of effect. St. Albans, Holborn; the great church designed by
Mr. Butterfield, in Margaret street; Mr. Street's church near Vincent
square, Westminster; and several churches of Mr. Brooks', such as he was
kind enough to enable me to illustrate tonight, may be mentioned as
examples of the sort. Mr. Waterhouse has built an elaborate
Congregational church at Hampstead, which shows the use with which such
effects of color may be obtained in interiors, and has kindly lent some
drawings. Mr. Pearson's church at Kilburn may also be referred to as a
fine example of brick vaulting. Brick and terra cotta seem to have a
natural affinity for one another. Terra cotta is no more than a refined
brick, made of the same sort of material, only in every respect more
carefully, and kiln baked. Its similarity to brick is such that there is
no sense of incongruity if moulded or carved brickwork and terra cotta
are both employed in the same building, and this can hardly be said to
be the case if the attempt is made to combine ornamental brickwork and
stone ornaments.

At South Kensington, a whole group of examples of brickwork with terra
cotta meet us. The Natural History Museum, the finest of them all, is
hardly fit for our present purpose, as it is as completely encased in
terra cotta as the fronts of the buildings in this avenue are in stone.
But here are the Albert Hall, a fine specimen of mass and effect; the
City and Guilds Institute; the College of Music, and some private houses
and blocks of flats, all in red brick with terra cotta, and all showing
the happy manner in which the two materials can be blended. In most of
them there is a contrast of color; but Mr. Waterhouse, in the Technical
Institute, has employed red terra cotta with red bricks, as he also has
done in his fine St. Paul's School at Hammersmith, and Mr. Norman Shaw
has, in his fine pile of buildings in St. James' street. This
combination--namely, brick and terra cotta--I look upon as the best for
withstanding the London climate, and for making full use of the
capabilities of brickwork that can be employed, and I have no doubt that
in the future it will be frequently resorted to. Some of those examples
also show the introduction of cast ornaments, and others the employment
of carving as means of enriching the surface of brick walls with
excellent effect. Here we must leave the subject; but in closing, I
cannot forbear pointing to the art of the bricklayer as a fine example
of what may be accomplished by steady perseverance. Every brick in the
miles of viaducts or tunnels, houses, or public buildings, to which we
have made allusion, was laid separately, and it is only steady
perseverance, brick after brick, on the part of the bricklayer, which
could have raised these great masses of work. Let me add that no one
brick out of the many laid is of no importance. Some time ago a great
fire occurred in a public asylum, and about L2,000 of damage was done,
and the lives of many of the inmates endangered. When the origin of this
fire came to be traced out, it was found that it was due to one brick
being left out in a flue. A penny would be a high estimate of the cost
of that brick and of the expense of laying it, yet through the neglect
of that pennyworth, L2,000 damage was done, and risk of human life was
run. I think there is a moral in this story which each of us can make
out if he will.

* * * * *

A fireproof whitewash can be readily made by adding one part silicate of
soda (or potash) to every five parts of whitewash. The addition of a
solution of alum to whitewash is recommended as a means to prevent the
rubbing off of the wash. A coating of a good glue size made by
dissolving half a pound of glue in a gallon of water is employed when
the wall is to be papered.

* * * * *


[Footnote: From a paper read before the recent meeting of the American
Institute of Electrical Engineers, New York, and reported in the
_Electrical World_.]


The actions produced and producible by the agency of alternating
currents of considerable energy are assuming greater importance in the
electric arts. I mean, of course, by the term alternating currents,
currents of electricity reversed at frequent intervals, so that a
positive flow is succeeded by a negative flow, and that again by a
positive flow, such reversals occurring many times in a second, so that
the curve of current of electromotive force will, if plotted, be a wave
line, the amplitude of which is the arithmetical sum of the positive and
negative maxima of current or electromotive force, as the case may be,
while a horizontal middle line joins the zero points of current or
electromotive force.

[Illustration: FIG. 1]

It is well known that such a current passing in a coil or conductor laid
parallel with or in inductive relation to a second coil or conductor,
will induce in the second conductor, if on open circuit, alternating
electromotive forces, and that if its terminals be closed or joined,
alternating currents of the same rhythm, period, or pitch, will
circulate in the second conductor. This is the action occurring in any
induction coil whose primary wire is traversed by alternating currents,
and whose secondary wire is closed either upon itself directly or
through a resistance. What I desire to draw attention to in the present
paper are the mechanical actions of attraction and repulsion which will
be exhibited between the two conductors, and the novel results which may
be obtained by modifications in the relative dispositions of the two

[Illustration: FIG. 2.]

In 1884, while preparing for the International Electrical Exhibition at
Philadelphia, we had occasion to construct a large electro-magnet, the
cores of which were about six inches in diameter and about twenty inches
long. They were made of bundles of iron rod of about 5/16 inch diameter.
When complete, the magnet was energized by the current of a dynamo
giving continuous currents, and it exhibited the usual powerful magnetic
effects. It was found also that a disk of sheet copper, of about 1/16
inch thickness and 10 inches in diameter, if dropped flat against a pole
of the magnet, would settle down softly upon it, being retarded by the
development of currents in the disk due to its movement in a strong
magnetic field, and which currents were of opposite direction to those
in the coils of the magnet. In fact, it was impossible to strike the
magnet pole a sharp blow with the disk, even when the attempt was made
by holding one edge of the disk in the hand and bringing it down
forcibly toward the magnet. In attempting to raise the disk quickly off
the pole, a similar but opposite action of resistance to movement took
place, showing the development of currents in the same direction to
those in the coils of the magnet, and which currents, of course, would
cause attraction as a result.

[Illustration: Fig. 3]

The experiment was, however, varied, as in Fig. 1. The disk, D, was held
over the magnet pole, as shown, and the current in the magnet coils cut
off by shunting them. There was felt an attraction of the disk or a dip
toward the pole. The current was then put on by opening the shunting
switch, and a repulsive action or lift of the disk was felt. The actions
just described are what would be expected in such a case, for when
attraction took place, currents had been induced in the disk, D, in the
same direction as those in the magnet coils beneath it, and when
repulsion took place the induced current in the disk was of opposite
character or direction to that in the coils.

[Illustration: Fig. 4]

Now let us imagine the current in the magnet coils to be not only cut
off, but reversed back and forth.

For the reasons just given, we will find that the disk, D, is attracted
and repelled alternately; for, whenever the currents induced in it are
of the same direction with those in the inducing or magnet coil,
attraction will ensue, and when they are opposite in direction,
repulsion will be produced. Moreover, the repulsion will be produced
when the current in the magnet coil is rising to a maximum in either
direction, and attraction will be the result when the current of either
direction is falling to zero, since in the former case opposite currents
are induced in the disk, D, in accordance with well known laws, and in
the latter case currents of the same direction will exist in the disk,
D, and the magnet coil. The disk might, of course, be replaced by a ring
of copper or other good conductor, or by a closed coil of bare or
insulated wire, or by a series of disks, rings or coils superposed, and
the results would be the same. Thus far, indeed, we have nothing of a
particularly novel character, and, doubtless, other experimenters have
made very similar experiments and noted similar results to those

[Illustration: FIG. 5]

The account just given of the effects produced by alternating currents,
while true, is not the whole truth, and just here we may supplement it
by the following statements:

_An alternating current circuit or coil repels and attracts a closed
circuit or coil placed in direct or magnetic inductive relation
therewith; but the repulsive effect is in excess of the attractive

When the closed circuit or coil is so placed, and is of such low
resistance metal that a comparatively large current can circulate as an
induced current, so as to be subject to a large self-induction, the
repulsive far exceeds the attractive effort_.

For want of a better name, I shall call this excess of repulsive effect
the "electro-inductive repulsion" of the coils or circuits.

[Illustration: FIG. 6.]

This preponderating repulsive effect may be utilized or may show its
presence by producing movement or pressure in a given direction, by
producing angular deflection as of a pivoted body, or by producing
continuous rotation with a properly organized structure. Some of the
simple devices realizing the conditions I will now describe.

[Illustration: FIG. 7.]

In Fig. 2, C is a coil traversed by alternating currents. B is a copper
case or tube surrounding it, but not exactly over its center. The copper
tube, B, is fairly massive and is the seat of heavy induced currents.
There is a preponderance of repulsive action, tending to force the two
conductors apart in an axial line. The part, B, may be replaced by
concentric tubes slid one in the other, or by a pile of flat rings, or
by a closed coil of coarse or fine wire insulated, or not. If the coil,
C, or primary coil, is provided with an iron core such as a bundle of
fine iron wires, the effects are greatly increased in intensity, and the
repulsion with a strong primary current may become quite vigorous, many
pounds of thrust being producible by apparatus of quite moderate size.

The forms and relations of the two parts, C and B, may be greatly
modified, with the general result of a preponderance of repulsive action
when the alternating currents circulate.

Fig. 3 shows the part, B, of an internally tapered or coned form, and C
of an externally coned form, wound on an iron wire bundle, I. The action
in Fig. 2 may be said to be analogous to that of a plain solenoid with
its core, except that repulsion, and not attraction, is produced, while
that of Fig. 3 is more like the action of tapered or conically wound
solenoids and taper cores. Of course, it is unnecessary that both be
tapered. The effect of such shaping is simply to modify the range of
action and the amount of repulsive effort existing at different parts of
the range.

[Illustration: FIG. 8.]

In Fig. 4 the arrangement is modified so that the coil, C, is outside,
and the closed band or circuit, B, inside and around the core, I.
Electro-inductive repulsion is produced as before.

It will be evident that the repulsive actions will not be mechanically
manifested by axial movement or effort when the electrical middles of
the coils or circuits are coincident. In cylindrical coils in which the
current is uniformly distributed through all the parts of the conductor
section, what I here term the electrical middle, or the center of
gravity of the ampere turns of the coils, will be the plane at right
angles to its axis at its middle, that of B and C, in Fig. 4, being
indicated by a dotted line. To repeat, then, when the centers or center
planes of the conductors, Fig. 4, coincide, no indication of
electro-inductive repulsion is given, because it is mutually balanced in
all directions; but when the coils are displaced, a repulsion is
manifested, which reaches a maximum at a position depending on the
peculiarities of proportion and distribution of current at any time in
the two circuits or conductors.

[Illustration: FIG. 9.]

It is not my purpose now to discuss the ways of determining the
distribution of currents and mechanical effects, as that would extend
the present paper much beyond its intended limit. The forms and relative
arrangement of the two conductors may be greatly varied. In Fig. 5 the
parts are of equal diameter, one, B, being a closed ring, and the other,
C, being an annular coil placed parallel thereto; and an iron core or
wire bundle placed in the common axis of the two coils increases the
repulsive action. B may be simply a disk or plate of any form, without
greatly affecting the nature of the action produced. It may also be
composed of a pile of copper washers or a coil of wire, as before

[Illustration: FIG. 10.]

An arrangement of parts somewhat analogous to that of a horseshoe
electro magnet and armature is shown in Fig. 6. The alternating current
coils, C C', are wound upon an iron wire bundle bent into U form, and
opposite its poles is placed a pair of thick copper disks, B B', which
are attracted and repelled, but with an excess of repulsion depending on
their form, thickness, etc.

[Illustration: FIG. 11.]

If the iron core takes the form of that shown by I I, Fig. 7, such as a
cut ring with the coil, C, wound thereon, the insertion of a heavy
copper plate, B, into the slot or divided portion of the ring will be
opposed by a repulsive effort when alternating currents pass in C. This
was the first form of device in which I noticed the phenomenon of
repulsive preponderance in question. The tendency is to thrust the
plate, B, out of the slot in the ring excepting only when its center is
coincident with the magnetic axis joining the poles of the ring between
which B is placed.

If the axes of the conductors, Fig. 5, are not coincident, but
displaced, as in Fig. 8, then, besides a simple repulsion apart, there
is a lateral component or tendency, as indicated by the arrows. Akin to
this is the experiment illustrated in Fig. 9. Here the closed conductor,
B, is placed with its plane at right angles to that of C, wound on a
wire bundle. The part, B, tends to move toward the center of the coil,
C, so that its axis will be in the middle plane of C, transverse to the
core, as indicated by the dotted line. This leads us at once to another
class of actions, i.e., deflective actions.

[Illustration: FIG. 12.]

When one of the conductors, as B, Fig. 10, composed of a disk, or,
better, of a pile of thin copper disks, or of a closed coil of wire, is
mounted on an axis, X, transverse to the axis of coil, C, through which
coil the alternating current passes, a deflection of B to the position
indicated by dotted lines will take place, unless the plane of B is at
the start exactly coincident with that of C. If slightly inclined at the
start, deflection will be caused as stated. It matters not whether the
coil, C, incloses the part, B, or be inclosed by it, or whether the
coil, C, be pivoted and B fixed, or both be pivoted. In Fig. 11 the
coil, C, surrounds an iron wire core, and B is pivoted above it, as
shown. It is deflected, as before, to the position indicated in dotted

[Illustration: FIG. 13]

It is important to remark here that in cases where deflection is to be
obtained, as in Figs. 10 and 11, B had best be made of a pile of thin
washers or a closed coil of insulated wire instead of a solid ring. This
avoids the lessening of effect which would come from the induction of
currents in the ring, B, in other directions than parallel to its

[Illustration: FIG. 14.]

We will now turn our attention to the explanation of the actions
exhibited, and afterward refer to their possible applications. It may be
stated as certainly true that were the induced currents in the closed
conductor unaffected by any self-induction, the only phenomena exhibited
would be alternate equal attractions and repulsions, because currents
would be induced in opposite directions to that of the primary current
when the latter current was changing from zero to maximum positive or
negative current, so producing repulsion; and would be induced in the
same direction when changing from maximum positive or negative value to
zero, so producing attraction.

This condition can be illustrated by a diagram, Fig. 12. Here the lines
of zero current are the horizontal straight lines. The wavy lines
represent the variations of current strength in each conductor, the
current in one direction being indicated by that portion of the curve
above the zero line, and in the other direction by that portion below
it. The vertical dotted lines simply mark off corresponding portions of
phase or succession of times.

[Illustration: FIG. 15]

Here it will be seen that in the positive primary current descending
from m, its maximum, to the zero line, the secondary current has risen
from its zero to m, its maximum. Attraction will therefore ensue, for
the currents are in the same direction in the two conductors. When the
primary current increases from zero to its negative maximum, n, the
positive current in the secondary closed circuit will be decreasing from
m, its positive maximum, to zero; but, as the currents are in opposite
directions, repulsion will occur. These actions of attraction and
repulsion will be reproduced continually, there being a repulsion, then
an attraction, then a repulsion, and again an attraction, during one
complete wave of the primary current. The letters, r, a, at the foot of
the diagram, Fig. 12, indicate this succession.

In reality, however, the effects of self-induction in causing a lag,
shift, or retardation of phase in the secondary current will
considerably modify the results, and especially so when the secondary
conductor is constructed so as to give to such self-induction a large
value. In other words, the maxima of the primary or inducing current
will no longer be found coincident with the zero points of the secondary
currents. The effect will be the same as if the line representing the
wave of the secondary current in Fig. 12 had been shifted forward to a
greater or less extent. This is indicated in diagram, Fig. 13. It gives
doubtless an exaggerated view of the action, though from the effects of
repulsion which I have produced, I should say it is by no means an
unrealizable condition.

[Illustration: Fig. 16.]

It will be noticed that the period during which the currents are
opposite, and during which repulsion can take place, is lengthened at
the expense of the period during which the currents are in the same
direction for attractive action. These differing periods are marked r,
a, etc., or the period during which _repulsion_ exists is from the zero
of the primary or inducing current to the succeeding zero of the
secondary or induced current; and the period during which _attraction_
exists is from the zero of the induced current to the zero of inducing

But far more important still in giving prominence to the repulsive
effect than this difference of effective period is the fact that during
the period of repulsion both the inducing and induced currents have
their greatest values, while during the period of attraction the
currents are of small amounts comparatively. This condition may be
otherwise expressed by saying that the period during which repulsion
occurs includes all the maxima of current, while the period of
attraction includes no maxima. There is then a _repulsion due to the
summative effects of strong opposite currents_ for a _lengthened
period_, against an _attraction_ due to the summative effects of _weak
currents_ of the _same direction_ during a _shortened period_, the
resultant effect being a greatly _preponderating_ repulsion.

It is now not difficult to understand all the actions before described
as obtained with the varied relations of coils, magnetic fields, and
closed circuits. It will be easily understood, also, that an alternating
magnetic field is in all respects the same as an alternating current
coil in producing repulsion on the closed conductor, because the
repulsions between the two conductors are the result of magnetic
repulsions arising from opposing fields produced by the coils when the
currents are of opposite directions in them.

Thus far I have applied the repulsive action described in the
construction of alternating current indicators, alternating current arc
lamps, regulating devices for alternating currents, and to rotary motors
for such currents. For current indicators, a pivoted or suspended copper
band or ring composed of thin washers piled together and insulated from
one another, and made to carry a pointer or index has been placed in the
axis of a coil conveying alternating currents whose amount or potential
is to be indicated. Gravity or a spring is used to bring the index to
the zero of a divided scale, at which time the plane of the copper ring
or band makes an angle of, say, 15 degrees to 20 degrees with the plane
of the coil. This angle is increased by deflection more or less great,
according to the current traversing the coil. The instrument can be
calibrated for set conditions of use. Time would not permit of a full
description of these arrangements as made up to the present.

In arc lamps the magnet for forming the arc can be composed of a closed
conductor, a coil for the passage of current, and an iron wire core. The
repulsive action upon the closed conductor lifts and regulates the
carbons in much the same manner that electro magnets do when continuous
currents are used. The electro-inductive repulsive action has also been
applied to regulating devices for alternating currents, with the details
of which I cannot now deal.

For the construction of an alternating current motor which can be
started from a state of rest the principle has also been applied, and it
may here be remarked that a number of designs of such motors is

One of the simplest is as follows: The coils, C, Fig. 14, are traversed
by an alternating current and are placed over a coil, B, mounted upon a
horizontal axis, transverse to the axis of the coil, C. The terminals of
the coil, B, which is wound with insulated wire, are carried to a
commutator, the brushes being connected by a wire, as indicated. The
commutator is so constructed as to keep the coil, B, on short circuit
from the position of coincidence with the plane of C to the position
where the plane of B is at right angles to that of C; and to keep the
coil, B, open-circuited from the right-angled position, or thereabouts,
to the position of parallel or coincident planes. The deflective
repulsion exhibited by B will, when its circuit is completed by the
commutator and brushes, as described, act to place its plane at right
angles to that of C; but being then open-circuited, its momentum carries
it to the position just past parallelism, at which moment it is again
short-circuited, and so on. It is capable of very rapid rotation, but
its energy is small. I have, however, extended the principle to the
construction of more complete apparatus. One form has its revolving
portion or armature composed of a number of sheet iron disks wound as
usual with three coils crossing near the shaft. The commutator is
arranged to short-circuit each of these coils in succession, and twice
in a revolution, and for a period of 90-degrees of rotation each. The
field coils surround the armature, and there is a laminated iron field
structure completing the magnetic circuit. I may say here that
surrounding the armature of a dynamo by the field coils, though very
recently put forth as a new departure, was described in various
Thomson-Houston patents, and to a certain extent all Thomson-Houston
machines embody this feature.

Figs. 15 and 16 will give an idea of the construction of the motor
referred to. CC' are the field coils or inducing coils, which alone are
put into the alternating current circuit. II is a mass of laminated
iron, in the interior of which the armature revolves, with its three
coils, B, B squared, B cubed, wound on a core of sheet iron disks. The commutator
short-circuits the armature coils in succession in the proper positions
to utilize the repulsive effect set up by the currents which are induced
in them by the alternations in the field coils. The motor has no dead
point, and will start from a state of rest and give out considerable
power, but with what economy is not yet known.

A curious property of the machine is that at a certain speed, depending
on the rapidity of the alternations in the coil, C, a continuous current
passes from one commutator brush to the other, and it will energize
electro magnets and perform other actions of direct currents. Here we
have, then, a means of inducing direct currents from alternating
currents. To control the speed and keep it at that required for the
purpose, we have only to properly gear the motor to another of the
ordinary type for alternating currents, namely, an alternating-current
dynamo used as a motor. The charging of storage batteries would not be
difficult with such a machine, even from an alternating-current line,
though the losses might be considerable.

* * * * *



_First Annual Report_.

Dr. Henry Draper, in 1872, was the first to photograph the lines of a
stellar spectrum. His investigation, pursued for many years with great
skill and ingenuity, was most unfortunately interrupted in 1882 by his

The recent advances in dry-plate photography have vastly increased our
powers of dealing with this subject. Early in 1886, accordingly, Mrs.
Draper made a liberal provision for carrying on this investigation at
the Harvard College Observatory, as a memorial to her husband. The
results attained are described below, and show that an opportunity is
open for a very important and extensive investigation in this branch of
astronomical physics. Mrs. Draper has accordingly decided greatly to
extend the original plan of work, and to have it conducted on a scale
suited to its importance. The attempt will be made to include all
portions of the subject, so that the final results shall form a complete
discussion of the constitution and conditions of the stars, as revealed
by their spectra, so far as present scientific methods permit. It is
hoped that a greater advance will thus be made than if the subject was
divided among several institutions, or than if a broader range of
astronomical study was attempted.

It is expected that a station to be established in the southern
hemisphere will permit the work to be extended so that a similar method
of study may be applied to stars in all parts of the sky. The
investigations already undertaken, and described below more in detail,
include a catalogue of the spectra of all stars north of--24 deg. of the
sixth magnitude and brighter, a more extensive catalogue of spectra of
stars brighter than the eighth magnitude, and a detailed study of the
spectra of the bright stars.

This last will include a classification of the spectra, a determination
of the wave lengths of the lines, a comparison with terrestrial spectra,
and an application of the results to the measurement of the approach and
recession of the stars. A special photographic investigation will also
be undertaken of the spectra of the banded stars, and of the ends of the
spectra of the bright stars.

The instruments employed are an eight inch Voigtlander photographic
lens, reground by Alvan Clark & Sons, and Dr. Draper's 11 inch
photographic lens, for which Mrs. Draper has provided a new mounting and
observatory. The 15 inch refractor belonging to the Harvard College
Observatory has also been employed in various experiments with a slit
spectroscope, and is again being used as described below. Mrs. Draper
has decided to send to Cambridge a 28 inch reflector and its mountings,
and a 15 inch mirror, which is one of the most perfect reflectors
constructed by Dr. Draper, and with which his photograph of the moon was
taken. The first two instruments mentioned above have been kept at work
during the first part of every clear night for several months. It is now
intended that at least three telescopes shall be used during the whole
night, until the work is interrupted by daylight.

The spectra have been produced by placing in front of the telescope a
large prism, thus returning to the method originally employed by
Fraunhofer in the first study of stellar spectra. Four 15 deg. prisms have
been constructed, the three largest having clear apertures of nearly
eleven inches, and the fourth being somewhat smaller. The entire weight
of these prisms exceeds a hundred pounds, and they fill a brass cubical
box a foot on each side. The spectrum of a star formed by this apparatus
is extremely narrow when the telescope is driven by clockwork in the
usual way. A motion is accordingly given to the telescope slightly
differing from that of the earth by means of a secondary clock
controlling it electrically. The spectrum is thus spread into a band,
having a width proportional to the time of exposure and to the rate of
the controlling clock.

This band is generally not uniformly dense. It exhibits lines
perpendicular to the refracting edge of the prism, such as are produced
in the field of an ordinary spectroscope by particles of dust upon the
slit. In the present case, these lines may be due to variations in the
transparency of the air during the time of exposure, or to instrumental
causes, such as irregular running of the driving clock, or slight
changes in the motion of the telescope, resulting from the manner in
which its polar axis is supported.

These instrumental defects may be too small to be detected in ordinary
micrometric or photographic observations, and still sufficient to affect
the photographs just described.

A method of enlargement has been tried which gives very satisfactory
results, and removes the lines above mentioned as defects in the
negatives. A cylindrical lens is placed close to the enlarging lens,
with its axis parallel to the length of the spectrum. In the apparatus
actually employed, the length of the spectrum, and with it the
dispersion, is increased five times, while the breadth is made in all
cases about four inches. The advantage of this arrangement is that it
greatly reduces the difficulty arising from the feeble light of the
star. Until very lately, the spectra in the original negatives were made
very narrow, since otherwise the intensity of the starlight would have
been insufficient to produce the proper decomposition of the silver
particles. The enlargement being made by daylight, the vast amount of
energy then available is controlled by the original negative, the action
of which may be compared to that of a telegraphic relay. The copies
therefore represent many hundred times the original energy received from
the stars. If care is not taken, the dust and irregularities of the film
will give trouble, each foreign particle appearing as a fine spectral

Our methods of enlargement have been considered, and some of them tried,
with the object of removing the irregularities of the original spectra
without introducing new defects. For instance, the sensitive plate may
be moved during the enlargement in the direction of the spectral lines;
a slit parallel to the lines may be used as the source of light, and the
original negative separated by a small interval from the plate used for
the copy; or two cylindrical lenses may be used, with their axes
perpendicular to each other. In some of these ways the lines due to dust
might either be avoided or so much reduced in length as not to resemble
the true lines of the spectrum.

The 15 inch refractor is now being used with a modification of the
apparatus employed by Dr. Draper in his first experiments--a slit
spectroscope from which the slit has been removed. A concave lens has
been substituted for the collimator and slit, and besides other
advantages, a great saving in length is secured by this change. It is
proposed to apply this method to the 28 inch reflector, thus utilizing
its great power of gathering light.

[A description of an accompanying plate here follows, which is omitted,
as the plate cannot be easily reproduced for ordinary press printing.]

The results to be derived from the large number of photographs already
obtained can only be stated after a long series of measurements and a
careful reduction and discussion of them. An inspection of the plates,
however, shows some points of interest. A photograph of _a Cygni_, taken
November, 26, 1886, shows that the H line is double, its two components
having a difference in wave length of about one ten-millionth of a
millimeter. A photograph of _o Ceti_ shows that the lines G and _h_ are
bright, as are also four of the ultra-violet lines characteristic of
spectra of the first type. The H and K lines in this spectrum are dark,
showing that they probably do not belong to that series of lines. The
star near _[chi]' Orionis_, discovered by Gore, in December, 1885, gives
a similar spectrum, which affords additional evidence that it is a
variable of the same class as _o Ceti_. Spectra of _Sirius_ show a large
number of faint lines besides the well-known broad lines.

The dispersion employed in any normal map of the spectrum may be
expressed by its scale, that is, by the ratio of the wave length as
represented to the actual wave length. It will be more convenient to
divide these ratios by one million, to avoid the large numbers otherwise
involved. If one millionth of a millimeter is taken as the unit of wave
length, the length of this unit on the map in millimeters will give the
same measure of the dispersion as that just described. When the map is
not normal, the dispersion of course varies in different parts. It
increases rapidly toward the violet end when the spectrum is formed by a
prism. Accordingly, in this case the dispersion given will be that of
the point whose wave length is 400.

This point lies near the middle of the photographic spectrum when a
prism is used, and is not far from the H line. The dispersion may
accordingly be found with sufficient accuracy by measuring the interval
between the H and K lines, and dividing the result in millimeters by
3.4, since the difference in their wave lengths equals this quantity.
The following examples serve to illustrate the dispersion expressed in
this way: Angstrom, Cornu, 10; Draper, photographer of normal solar
spectrum, 3.1 and 5.2; Rowland, 23, 33, and 46; Draper, stellar spectra,
0.16; Huggins, 0.1.

The most rapid plates are needed in this work, other considerations
being generally of less importance. Accordingly, the Allen and Rowell
extra quick plates have been used until recently. It was found, however,
that they were surpassed by the Seed plates No. 21, which were
accordingly substituted for them early in December. Recognizing the
importance of supplying this demand for the most sensitive plates
possible, the Seed Company have recently succeeded in making still more
sensitive plates, which we are now using. The limit does not seem to be
reached even yet. Plates could easily be handled if the sensitiveness
were increased tenfold. A vast increase in the results may be
anticipated with each improvement of the plates in this respect.
Apparatus for testing plates, which is believed to be much more accurate
than that ordinarily employed, is in course of preparation. It is
expected that a very precise determination will be made of the rapidity
of the plates employed. Makers of very rapid plates are invited to send
specimens for trial.

The photographic work has been done by Mr. W.P. Gerrish, who has also
rendered important assistance in other parts of the investigation. He
has shown great skill in various experiments which have been tried, and
in the use of various novel and delicate instruments. Many of the
experimental difficulties could not have been overcome but for the
untiring skill and perseverance of Mr. George B. Clark, of the firm of
Alvan Clark & Sons, by whom all the large instruments have been

The progress of the various investigations which are to form a part of
this work is given below:

1. _Catalogue of Spectra of Bright Stars_.--This is a continuation of
the work undertaken with the aid of an appropriation from the Bache
fund, and described in the Memoirs of the American Academy, vol. xi., p.
210. The 8 inch telescope is used, each photograph covering a region of
10 deg. square. The exposures for equatorial stars last for five minutes,
and the rate of the clock is such that the spectra have a width of about
0.1 cm. The length of the spectra is about 1.2 cm. for the brighter, and
0.6 cm. for the fainter stars. The dispersion of the scale proposed
above is 0.1.

The spectra of all stars of the sixth magnitude and brighter will
generally be found upon these plates, except in the case of red stars.
Many fainter blue stars also appear. Three or four exposures are made
upon a single plate. The entire sky north of -24 deg. would be covered
twice, according to this plan, with 180 plates and 690 exposures. It is
found preferable in some cases to make only two exposures; and when the
plate appears to be a poor one, the work is repeated. The number of
plates is therefore increased. Last summer the plates appeared to be
giving poor results. Dust on the prisms seemed to be the explanation of
this difficulty. Many regions were reobserved on this account. The first
cycle, covering the entire sky from zero to twenty-four hours of right
ascension, has been completed.

The work will be finished during the coming year by a second cycle of
observations, which has already been begun. The first cycle contains 257
plates, all of which have been measured, and a large part of the
reduction completed. 8,313 spectra have been measured on them, nearly
all of which have been identified, and the places of a greater portion
of the stars brought forward to the year 1900, and entered in catalogue
form. In the second cycle, 64 plates have been taken, and about as many
more will be required. 51 plates have been measured and identified,
including 2,974 spectra. A study of the photographic brightness and
distribution of the light in the spectra will also be made.

The results will be published in the form of a catalogue resembling the
Photometric Catalogue given in volume xiv. of the Annals of Harvard
College Observatory. It will contain the approximate place of each star
for 1900, its designation, the character of the spectrum as derived from
each of the plates in which it was photographed, the references to these
plates, and the photographic brightness of the star.

2. _Catalogue of Spectra of Faint Stars_.--This work resembles the
preceding, but is much more extensive. The same instrument is used, but
each region has an exposure of an hour, the rate of the clock being such
that the width of the spectrum will be as before 0.1 cm. Many stars of
the ninth magnitude will thus be included, and nearly all brighter than
the eighth. In one case, over three hundred spectra are shown on a
single plate. This work has been carried on only in the intervals when
the telescope was not needed for other purposes. 99 plates have,
however, been obtained, and on these 4,442 spectra have been measured.
It is proposed to complete the equatorial zones first, gradually
extending the work northward. In all, 15,729 spectra of bright and faint
stars have been measured.

3. _Detailed Study of the Spectra of the Brighter Stars_.--This work has
been carried on with the 11 inch photographic telescope used by Dr.
Draper in his later researches. A wooden observatory was constructed
about 20 feet square. This was surmounted by a dome having a clear
diameter of 18 feet on the inside. The dome had a wooden frame, sheathed
and covered with canvas. It rested on eight cast iron wheels, and was
easily moved by hand, the power being directly applied. Work was begun
upon it in June, and the first observations were made with the telescope
in October.

Two prisms were formed by splitting a thick plate of glass diagonally.
These gave such good results that two others were made in the same way,
and the entire battery of four prisms is ordinarily used. The safety and
convenience of handling the prisms is greatly increased by placing them
in square brass boxes, each of which slides into place like a drawer.
Any combination of the prisms may thus be employed. As is usual in such
an investigation, a great variety of difficulties have been encountered,
and the most important of them have now been overcome.

4. _Faint Stellar Spectra_.--The 28 inch reflector will be used for the
study of the spectra of the faint stars, and also for the fainter
portions near the ends of the spectra of the brighter stars. The form of
spectroscope mentioned above, in which the collimator and slit are
replaced by a concave lens, will be tried. The objects to be examined
are, first, the stars known to be variable, with the expectation that
some evidence may be afforded of the cause of the variation. The stars
whose spectrum is known to be banded, to contain bright lines, or to be
peculiar in other respects, will also be examined systematically.
Experiments will also be tried with orthochromatic plates and the use of
a colored absorbing medium, in order to photograph the red portions of
the spectra of the bright stars. Quartz will also be tried to extend the
images toward the ultra-violet.

5. _Absorption Spectra_.--The ordinary form of comparison spectrum
cannot be employed on account of the absence of a slit. The most
promising method of determining the wave lengths of the stellar spectra
is to interpose some absorbent medium. Experiments are in progress with
hyponitric fumes and other substances. A tank containing one of these
materials is interposed and the spectra photographed through it. The
stellar spectra will then be traversed by lines resulting from the
absorption of the media thus interposed, and, after their wave lengths
are once determined, they serve as a precise standard to which the
stellar lines may be referred. The absorption lines of the terrestrial
atmosphere would form the best standard for this purpose if those which
are sufficiently fine can be photographed.

6. _Wave Lengths_.--The determination of the wave lengths of the lines
in the stellar spectra will form an important part of the work which has
not yet been begun. The approximate wave lengths can readily be found
from a comparison with the solar spectrum, a sufficient number of solar
lines being present in most stellar spectra. If, then, satisfactory
results are obtained in the preceding investigation, the motion of the
stars can probably be determined with a high degree of precision. The
identification of the lines with those of terrestrial substances will of
course form a part of the work, but the details will be considered

From the above statement it will be seen that photographic apparatus has
been furnished on a scale unequaled elsewhere. But what is more
important, Mrs. Draper has not only provided the means for keeping these
instruments actively employed, several of them during the whole of every
clear night, but also of reducing the results by a considerable force of
computers, and of publishing them in a suitable form. A field of work of
great extent and promise is open, and there seems to be an opportunity
to erect to the name of Dr. Henry Draper a memorial such as heretofore
no astronomer has received. One cannot but hope that such an example may
be imitated in other departments of astronomy, and that hereafter other
names may be commemorated, not by a needless duplication of unsupported
observatories, but by the more lasting monuments of useful work


_Director of Harvard College Observatory_.

Cambridge, Mass., U.S.A., March 1, 1887.

* * * * *


The dark bay colt Merry Hampton had never run in public before winning
the Derby on the 25th of May last. This colt, by Hampton out of Doll
Tear-sheet, was one of Mr. Crowther Harrison's draught of yearlings sent
up to the Doncaster sales in 1885, and fell to the bid of Mr. T. Spence,
acting for Mr. Abingdon, for 3,100 guineas. The Oaks, on May 27, was won
by a daughter of the same sire. Merry Hampton is to compete for the
Grand Prize of Paris and for the St. Leger. He has also liabilities in
the Thirty-ninth Triennial and Grand Duke Michael stakes at Newmarket,
First October; Newmarket Derby at the Second October; Ascot Derby and
Twenty-fifth New Biennial; Drawing-room stakes at Goodwood; Great
International Breeders' Foal stakes at Kempton Park, August; North Derby
at Newcastle, Summer; St. George stakes at Liverpool, July; Bickerstaffe
stakes and St. Leger at Liverpool, August; Midland Derby stakes at
Leicester, July; and Ebor St. Leger at York, August; in addition to the
following races in 1888: Champion stakes at Newmarket, Second October;
Rous Memorial and Hardwicke stakes at Ascot, and Eclipse stakes at
Sandown Park, Second Summer. Merry Hampton's name also appears in the
Kempton Park Royal stakes of 10,000 sovereigns at the Spring Meeting of
1889.--_Ill. London News_.


* * * * *


At the extreme south of the presidency of Bombay, separating the
district of Kanara from the territory of Mysore, are the too little
known Falls of Gairsoppa.

Far higher than Niagara, four distinct divisions of the river Shiravatti
(traditionally created by a cleft made by the arrow of the great god
Rama) fall over a precipice of gneiss rock into an abyss eight hundred
feet below. Each of these cataracts differs in type of flow.

The "Rajah," eight hundred and thirty feet, and at a breadth of
fifty-six, shoots silent and sheer over an uplifted lip of rock in the
bed of the stream, casting a dark shadow behind him when faced by the
sun; the "Roarer" makes noise enough in its headlong rush to vibrate the
strong, stone-built travelers' bungalow on the heights above; the
"Rocket" is straight in descent, and, as a commentator has already
remarked, as much like a rocket as anything else; and "La Dame Blanche,"
a triptych of rhythmical flow, spreads a dainty, silky, sheen of white,
whispering, glistening, softly falling water over a slightly shelving
width of rock, touched here and there with prismatic color and strong


The Falls From Below. The Falls From Above.]

At the bottom of the chasm, seven hundred feet across, and stretching
over a muddy, turbulent, seething cauldron of spray, a brilliantly
distinct rainbow in the full light of day may be seen with its scarcely
less glorious reflection, dazzlingly beautiful.

In these regions 210 inches of rain is an average downpour for the
monsoon between May and October, the heaviest fall being generally in
July. The cataracts then become frequently confluent, though not more
picturesque. They are then too difficult of access, and the whole
district is very malarious. December and January are the best months for
travelers, before the dry season fairly sets in again, during which
there is but little water, even insufficient to form four distinct

The best route to them is from Bombay to Honaurre by sea, _via_ Kawai,
and on to Old Gairsoppa by river boat and palanquin to the "Jog," as the
special points of interest (the "Falls") are called by the Kanarese.

To the enthusiastic shikari, however, the way from Hubli (on the
Southern Mahratta Railway, easily reached by G.I.P. line from Bombay),
taking him, as it does, through the very happiest hunting grounds of the
presidency, where all game, small and large, abounds, will have
attraction enough; and at Giddapur, the last stage, within twelve miles
of the Falls, there is a courteous English-speaking native magistrate,
willing and able to help the traveler on his way. Our engravings are
from drawings by Mr. J.E. Page, C.E.--_London Graphic_.

* * * * *


As the last of a course of lectures upon "Recent Scientific Researches
in Australasia," Dr. R. Von Ledenfeld lately delivered a lecture at the
Royal Institution, upon "Recent Additions to our Knowledge of Sponges."
The lecturer did not confine himself to the sponges of Australia alone,
but gave a _resume_ of the results of recent investigations on sponges,
together with several new interesting details observed more especially
in studying the growth of Australian sponges. With a passing reference
to some peculiarities of the lower marine animals of the Australian
coast, Dr. Ledenfeld remarked upon the preponderance of sponges over
other forms of marine life in that part of the world. It has long been a
point of discussion as to whether sponges belong to the vegetable or
animal kingdom, but naturalists are now generally agreed in regarding
them as animals, a conclusion, the lecturer remarked, that Aristotle had
also arrived at.

Sponges grow in a variety of more or less irregular shapes, but it has
been observed that the most regular structures occur in the calcareous
species. As to color, Dr. Ledenfeld remarked that some of the Australian
sponges are of exceptionally brilliant hues, while others range from the
black of the common sponge _(Euspongia officinalis)_ to a pure white.
Also, it may be remarked, the sponges growing in deep water are of less
decided color and more elastic in character than those living in shallow
water, and from the last named quality are more valuable in commerce.
The irregular honeycombed appearance of the sponge is due to a most
complicated canal system, consisting of a series of chambers through
which the water is drawn by the animal in always the same direction.

The inhalent pores are very minute, and open into small subdermal
cavities which communicate by means of interradial tubes with the
ciliated chambers, the latter being very small ramifications of the
interradial channels, and in them the movement causing the current of
water is maintained. From hence all faecal and other matter is
discharged through the oscula, the larger openings observed on the
surface of the sponge. Dr. Ledenfeld showed the different parts of
sponges by means of microscopic slides thrown on to a screen, and also
the shape and arrangement of the chambers in different species. The
ciliated chambers especially attracted attention. They are very small
and circular, and the interior is clothed with cells very similar to the
cilia cells in higher animal life.

These cells are arranged around the ciliated chambers in the form of a
collar, and from each cell flagella protrude, which are in continual
motion. These flagella, like bats' wings, are capable of being bent in
only one direction, so that, in the course of their pendulum-like
motion, in the movement one way the flagella are bent, while in the
return movement they remain stiff, thus causing a current of water
always flowing in one and the same direction. These ciliated chambers
are easily detected in the sponge by means of a microscope, as they
appear more highly colored. After the lecturer had thus given a general
outline of the structure of the sponge, he drew attention to the
character of its food and its method of digestion. It is not known
exactly what the sponge lives upon, but if upon other animals they must
be necessarily very small, owing to the size of its inhalent pores.

The sponge, like the tape-worm, has no stomach, but must absorb its food
through the outer skin from matter in a soluble state, similarly to the
roots of trees. This process of absorption is probably accomplished in
the interradial or ciliated chambers, more probably in the former, as
the latter are generally considered excretory in function. Lime or
silica must also be absorbed from the water by most sponges in order to
make up the skeleton. The skeleton of calcareous sponges consists of a
number of spicules composed of carbonate of lime. These spicules are of
very varied though regular shape, but ordinarily assume a rod-like
needle shape or else a stellate form. In silicious sponges the spicules
are composed of silica, and are generally deposited around axial rods in
concentric layers. The spicules are joined together and cemented by a
body that has been named "spongin," which has much the same chemical
composition as silk, and, like silk, is very elastic. In some varieties
of sponges, especially in the kinds which come into the market, the
skeleton is almost entirely composed of fibers of pure "spongin." These
fibers are so close together as to draw up water by capillary action,
and, indeed, a great deal in the value of a sponge depends upon the
fineness and tenuity of these fibers.

Dr. Ledenfeld again illustrated this stage of his lecture by means of a
number of microscopic slides in which the variety of shape and size of
these spicules and "spongin" fibers were shown. The spicules are some
crutch-like, others spined or echinated, while the deep-sea sponges
appear to grow long thick spicules, which attach the sponge to the
ground by means of grapnel-like ends. In some cases the skeleton seems
to be more or less replaced by sand, the small grains of which are
cemented together by the "spongin."

Dr. Ledenfeld then drew attention to the presence of more highly
developed organs in the sponge. Muscles pervade the whole tissue of the
sponge, but are found more particularly in the superficial parts. One
set of muscles affect the size of the inhalent pores, causing them to
contract or expand, while another set are able to close the pores
altogether, thus acting as a protection from the attack of an enemy. All
these muscles are composed of spindle shaped cells, which are capable of
spasmodic motion, but recently in an Australian sponge, the _Euspongia
canalicula_, the lecturer said he had observed muscles approaching very
nearly in character those of the human frame.

That sponges have nerves is a discovery of recent date by a member of
the Royal Microscopical Society. Dr. Ledenfeld also about the same time
found indications of the presence of a nervous system, but the form in
which he observed the nerves at first apparently differed from those
observed simultaneously. This difference, however, he afterward found to
be due to the manner in which the section had been prepared for
observation. The nerves consist of two cells at the base of a cone-like
projection on the epidermis, and from each cell a fiber runs to the
point of the cone, besides several others connecting them with the
interior of the sponge.

It is remarkable that here again Aristotle has predicted that sponges
have a nervous system, basing his statement on the fact that ancient
Greek mariners foretold storms by the alleged contraction of the sponge.
The reproductive organs of sponges are also very highly developed, and
both ova and spermatozoa are found throughout the sponge, though more
concentrated in the interior. The ova consist of spherical cells, while
the spermatozoa resemble an arrow-head in shape. It has not yet been
ascertained whether two sexes exist in sponges, or whether the ova and
spermatozoa are produced at different periods by the same sponge. When
the embryo has become partly developed, it detaches itself from the
parent sponge, and, issuing from the oscula, propels itself through the
water by means of a number of flagella.

Silicious spicules next appear in its structure, and it then attaches
itself to a rock and assumes its mature form. Sponges are most numerous
in the waters of the temperate and sub-tropical zones, and the
salt-water varieties are by far more numerous than the fresh water.
Thus, while there are not more than ten fresh-water species known, Dr.
Ledenfeld remarked that about one thousand species of salt-water sponges
had been recognized. Each species of the salt-water sponge is, however,
generally found only in limited areas, and very few, all of which
inhabit deep water, are cosmopolitan. This is the more remarkable as Dr.
Ledenfeld asserts that all the sponges inhabiting the rivers of
Australia are identical with the fresh-water sponges of Europe, and in
order to explain this fact he put forward a rather interesting theory.
He assumes that sponge life in rivers has been originally generated by
the introduction of a single, or at most two or three germs by means of
aquatic birds. The inbreeding consequent upon this paucity of sponge
life has produced a certain fixity of character in fresh-water sponges,
and is in direct opposition to the effects of hybridization in the
salt-water sponges, by which they have acquired the capacity of adapting
themselves to local circumstances.

* * * * *


Keeping the body clean is indispensable for the preservation of good
health, through obtaining an operation of the skin and expelling matter
whose presence aids in the development of diseases. It is unfortunately
necessary to say that, considering the population as a whole, the
proportion of those who take baths is very small. This is due to the
fact that the habit of cleanliness, which should become a necessity, has
not been early inculcated in every individual; and the reason that this
complement to education is not realized is because the means of
satisfying its exigencies are usually wanting.

We shall not speak of the improved processes that are used solely by the
rich or well-to-do, as these become impracticable where it is a question
of the working classes or of large masses of individuals. It is, in
fact, the last named category that interests us, and we are convinced
that if we get young soldiers and children to hold dirtiness in horror,
we shall be sure that they will later on take care of their bodies

The most tempting solution of this question of washing seems to be found
in the use of large pools of running tepid water; but such a process is
too costly for general use, and the most economical one, without doubt,
consists in giving tepid douches.

[Illustration: TEPID WATER DOUCHE]

To our knowledge, the only apparatus in this line that has been devised
was exhibited last year at the exhibition of hygiene in the Loban
barracks. It has been used daily for six years in several garrisons, and
therefore has the sanction of practice.

This apparatus, which is due to Mr. Herbet, consists of a steam boiler
and of an ejector fixed to a reservoir of water and provided with a
rubber tube to which a nozzle is attached. The steam generated in the
boiler passes into the ejector, sucks up the water and forces it out in
a tepid state.

The apparatus thus established did not sufficiently fulfill the purpose
for which it was designed. It was necessary to have a means of varying
the temperature of the water projected, according to the season and
temperature of the air, to have an instantaneous and simple method of
regulating the apparatus, that could be understood by any operator, and
to have the apparatus under the control of the person holding the
nozzle. These difficulties have been solved very simply by causing the
orifice of the nozzle to vary. This nozzle, from whence the jet escapes,
is formed of rings that screw together. When the nozzle is entire, the
jet escapes at a temperature of say 40 deg.. When the first ring is
unscrewed, the water will make its exit at a temperature of 38 deg.. In
order to lower the temperature still further, it is only necessary to
unscrew the other rings in succession, until the desired temperature has
been obtained.

As it is, the apparatus is rendering great services where it has been
introduced; for example, at Besancon and Belfort. It serves, in fact,
for an entire garrison, while that before, the washing was done in each
regiment, thus requiring the use of much space and causing much loss of

Eight men are washed at once for five minutes, say 96 men per hour.
Every minute the men turn right about face, and when they are in file
each rubs the other's back.

Twenty-two pounds of coal and 260 gallons of water are consumed per
hour, and the boiler produces 130 lb. of steam.--_Le Genie Civil_.

* * * * *


Being all of wood, it is easily made by any one who can use a few tools,
the only bit of lathe work necessary being the turned shoulder, K, of
polar axis. A is the baseboard, 9 in. by 5 in., near each corner of
which is inserted an ordinary wood screw, S S, for the purpose of
leveling the base, to which two side pieces are nailed, having the
angle, _x_, equal to the co-latitude of the place. On to these side
pieces is fastened another board, on which is marked the hour circle, F.
Through this board passes the lower end of the polar axis, having a
shoulder turned up on it at K, and is secured by a wooden collar and pin
underneath. On to the upper part of the polar axis is fastened the
declination circle, C, 51/2 in. diameter, made of 1/4 in. baywood, having
the outer rim of a thin compass card divided into degrees pasted on to
it. The hour circle, F, is half of a similar card, with the hours
painted underneath, and divided to 20 minutes. G is the hour index. D is
a straight wooden pointer, 12 in. long, having a piece of brass tube, E,
attached, and a small opening at J, into which is fixed the point of a
common pin by which to set the pointer in declination. H is a nut to
clamp pointer in position. By this simple toy affair I have often picked
up the planet Venus at midday when visible to the naked eye.--_T.R.
Clapham in English Mechanic_.

[Illustration: A STAR FINDER.]

* * * * *

The best mode of finding or tracing trichinae in pork by means of a
microscope is the following: Cut a very thin longitudinal slice of the
muscle by means of a very sharp knife or razor. Press it between two
glass slips, and examine by transmitted light, The coiled trichinae may
be readily distinguished from the muscle fiber.

* * * * *




Sent by mail, postage prepaid, to subscribers in any part of the United
States or Canada. Six dollars a year, sent, prepaid, to any foreign

All the back numbers of THE SUPPLEMENT, from the commencement, January
1, 1876, can be had. Price, 10 cents each.

All the back volumes of THE SUPPLEMENT can likewise be supplied. Two
volumes are issued yearly. Price of each volume, $2.50, stitched in
paper, or $3.50, bound in stiff covers.

SCIENTIFIC AMERICAN SUPPLEMENT, one year, postpaid, $7.00.

A liberal discount to booksellers, news agents, and canvassers.



* * * * *


In connection with the SCIENTIFIC AMERICAN, Messrs. MUNN & Co. are
Solicitors of American and Foreign Patents, have had 42 years'
experience, and now have the largest establishment in the world. Patents
are obtained on the best terms.

A special notice is made in the SCIENTIFIC AMERICAN of all Inventions
patented through this Agency, with the name and residence of the
Patentee. By the immense circulation thus given, public attention is
directed to the merits of the new patent, and sales or introduction
often easily effected.

Any person who has made a new discovery or invention can ascertain, free
of charge, whether a patent can probably be obtained, by writing to MUNN
& Co.

We also send free our Hand Book about the Patent Laws, Patents, Caveats,
Trade Marks, their costs, and how procured. Address


Branch Office, 622 and 624 F St., Washington, D.C.


Architects and Builders Edition.

$2.50 a Year. Single Copies, 25 Cents.

This is a Special Edition of THE SCIENTIFIC AMERICAN, issued monthly--on
the first day of the month. Each number contains about forty large
quarto pages, equal to about two hundred ordinary book pages, forming,
practically, a large and splendid MAGAZINE OF ARCHITECTURE, richly
adorned with _elegant plates in colors_ and with fine engravings;
illustrating the most interesting examples of modern Architectural
Construction and allied subjects.

A special feature is the presentation in each number of a variety of the
latest and best plans for private residences, city and country,
including those of very moderate cost as well as the more expensive.
Drawings in perspective and in color are given, together with full
Plans, Specifications, Costs, Bills of Estimate, and Sheets of Details.

No other building paper contains so many plans, details, and
specifications regularly presented as the SCIENTIFIC AMERICAN. Hundreds
of dwellings have already been erected on the various plans we have
issued during the past year, and many others are in process of

Architects, Builders, and Owners will find this work valuable in
furnishing fresh and useful suggestions. All who contemplate building or
improving homes, or erecting structures of any kind, have before them in
this work an almost _endless series of the latest and best examples_
from which to make selections, thus saving time and money.

Many other subjects, including Sewerage, Piping, Lighting, Warming,
Ventilating, Decorating, Laying out of Grounds, etc., are illustrated.
An extensive Compendium of Manufacturers Announcements is also given, in
which the most reliable and approved Building Materials, Goods,
Machines, Tools, and Appliances are described and illustrated, with
addresses of the makers, etc.

The fullness, richness, cheapness, and convenience of this work have won
for it the LARGEST CIRCULATION OF any Architectural publication in the

MUNN & CO., Publishers, 361 Broadway, New York.

A Catalogue of valuable books on Architecture, Building, Carpentry,
Masonry, Heating, Warming, Lighting, Ventilation, and all branches of
industry pertaining to the art of Building, is supplied free of charge,
sent to any address.

* * * * *


In connection with the publication of the BUILDING EDITION of the
SCIENTIFIC AMERICAN, Messrs. Munn & Co, furnish plans and specifications
for buildings of every kind, including Churches, Schools, Stores,
Dwellings, Carriage Houses, Barns, etc.

In this work they are assisted by able and experienced architects. Full
plans, details, and specifications for the various buildings illustrated
in this paper can be supplied.

Those who contemplate building, or who wish to alter, improve, extend,
or add to existing buildings, whether wings, porches, bay windows, or
attic rooms, are invited to communicate with the undersigned. Our work
extends to all parts of the country. Estimates, plans, and drawings,
promptly prepared. Terms moderate. Address

MUNN & CO., 361 Broadway, New York.

Book of the day:
Facebook Google Reddit StumbleUpon Twitter Pinterest