Scientific American Supplement, No. 303
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Various >> Scientific American Supplement, No. 303
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I emulsified the two together in the usual way, allowed the whole
to cool, and then poured the thin emulsion into about ten ounces
of alcohol, stirring the while. As I had anticipated, a flocculent
precipitate was formed, which settled to the bottom of the vessel in a
few minutes. This was, in fact, sensitive bromide of silver mixed with
a very small quantity of gelatine (about five per cent.), and could, I
found, be treated in the same manner as a bromide precipitate from
an aqueous solution; it might be washed, either by decantation or by
filtration, easily dried, and doubtless could, when dry, be kept for an
indefinite time, and be at any time used by mixing with gelatine and
water in any proportion thought fit.
I found that a less amount of gelatine than four grains to the ounce was
sufficient to carry the bromide down, while five grains to the ounce
carried it down in something which I considered too near an approach to
a plastic mass.
It will be noticed that in the experiments which I have described the
emulsion had not been boiled, so that the sensitiveness of the bromide
was probably not great. As the experiment was done in daylight it was
of no practical use for making emulsion; but I have since made several
batches in this manner and have found them most satisfactory.
When sensitiveness is sought by boiling I rind it necessary to add a
small quantity of gelatine after boiling and before precipitating, as
that which has been kept for some time at a high temperature seems to
have lost the viscosity necessary to carry down the silver bromide in
such a form that it can he easily separated from the alcohol and water.
The practical manner of making an emulsion by this method may be as
follows. Make up the following mixtures:
I.
Silver nitrate...........................................400 grains.
Water..................................................... 3 ounces.
II.
Ammonia bromide..........................................240 grains.
Gelatine..................................................24 grains
Water..................................................... 3 ounces.
Hydrochloric acid enough to slightly acidify the solution.
III.
Gelatine................................................. 20 grains.
Water.................................................... 1/2 ounce.
IV.
Hard gelatine (say Nelson's X opaque,
or Mr. A. L. Henderson's)................................240 grains.
Soft gelatine (Nelson's No.1)........................... 240 grains.
Water.....................................................24 ounces.
Nos. II., III., and IV. are allowed to stand until the gelatine is
softened. No. I is then warmed in a hock bottle until the gelatine is
just melted, when No. II. is poured into it, a little at a time, with
vigorous shaking, until the whole is emulsified. It is then transferred
to an ordinary jelly can, which is placed in a saucepan half full of
water over a ring Bunsen burner in the dark room, and boiled for half an
hour. It is then allowed to cool to about 100 deg. Fahr., when No. III. is
added. The whole is then allowed to get quite cool, when it is poured,
with stirring, into about one pint of methylated spirit. If it be wished
the precipitate may now be filtered out and washed at once like an
ordinary filtrate, but I prefer to allow it to settle, which it will do
in about five minutes. The supernatant fluid is then gently poured off.
This fluid will have the appearance of still containing a considerable
amount of the silver bromide; but if it be kept and filtered it will be
seen that the quantity is really so small that it may be disregarded. We
all know what an alarming quantity of silver seems to be going down the
sink when we wash vessels to which a very small quantity of emulsion is
adhering. If filtering be resorted to the liquid which comes through
will be quite clear. This was somewhat unexpected by me, as, if an
emulsion containing the whole of the gelatine be precipitated into
alcohol in the usual way, the alcohol becomes milky with a substance
which could not, I imagine, be filtered from it.
Two or three ounces of methylated spirit are now added to the vessel
containing the silver bromide, and the latter well mixed with it. This
makes the precipitate "firmer"--if such an expression be allowable--and
this time it will sink to the bottom almost immediately after the
stirring has ceased, and the alcohol may be poured off.
I consider that the bromide in this state is practically free from
soluble salts, but it may be washed with one or two changes of water if
desired.
No. IV. is now gently heated till the gelatine is melted and the
precipitate mixed with it. It must be kept warm for some time, and
shaken vigorously until all granularity has disappeared, This is, of
course, ascertained by placing a drop of the emulsion on a piece of
glass, and examining it. If it be wished to keep the bromide of silver
for future use it may be placed on a piece of muslin stretched in the
drying-box, when it will dry in a very short time; and, although I
cannot speak from experience on this point, it will, I have no doubt,
keep for an indefinite time so long as light is kept from it.
If it be desired the ammonio-nitrate method may be used instead of the
boiling one, although in my hands it does not give such sensitiveness.
If it be desired to use this method, solution Nos. I, II., and IV. are
made up exactly as for the boiling method, except that No. II. is not
acidified. Liquid ammonia is then poured with stirring into the silver
solution, until it blackens and again clears. Emulsification is
performed exactly as described above, but instead of boiling, the
emulsion is kept at a temperature of about 100 deg. Fahr. for half an hour,
when it is poured into the alcohol, no addition of gelatine being
previously made.
I think I may claim for the method which I have just described that it
is less troublesome and more certain than either the ordinary washing
method or the usual one of precipitating with alcohol, while it affords
an easy method of making sensitive silver bromide in such a form that it
can be more easily stored and afterwards manipulated than if it were in
the form of pellicle. The whole of the soluble salts are eliminated,
and also any gelatine which may have been destroyed in the cooking.
The amount of alcohol used is comparatively small; in fact, to prepare
silver bromide for a pint of emulsion very little more than a pint of
methylated spirit is required. Besides this I do not think that I would
be wrong in saying that the chance of green fog is reduced to a minimum.
Let me take this opportunity of thanking Captain Abney for his prompt
reply to my question about the connection between the proportion
of bromide to gelatine in emulsions, and the density of resulting
images.--_W. K. Burton, in British Journal of Photography_.
* * * * *
[Illustration: Old Wrought Iron Gates, Guildhall.]
* * * * *
THE POTTERY AND PORCELAIN INDUSTRIES OF JAPAN.
Japanese chronicles claim that the first pottery was made in the year
660 B.C.; it was not, however, until the Christian era that the art made
any considerable advances. In the year 1223 A.D., great improvements
were made in manufacture and decoration of the ware. From that date to
the sixteenth century the great potteries of Owari, Hizen, Mino, Kioto,
Kaga, and Satsuma were established. The Rahn-Yaki, or crackled ware, was
first made at Kioto, at the commencement of the sixteenth century. The
best old Hizen ware, that which is still the most admired, was made
at Arita Hizen, in 1580 to 1585; the old Satsuma dates from 1592.
Consul-General Van Buren states that porcelain clays are found in nearly
all parts of the country, and the different kinds are usually found
in close proximity, and close to canals and rivers, which is of
considerable advantage, as affording a means of transport. In all cases
every variety of clay used in the manufacture of pottery is found in a
natural state; there is no necessity to manufacture the quartzose or
fusible clays as is done in other parts of the world, and which adds
considerably to the cost of the ware. One of the peculiarities in the
clay found in Japan is that it contains both the fusible and infusible
materials in such proportions as to make a light, beautiful,
translucent, and durable porcelain. At Arita, in Hizen, there is a clay
found which contains 783/4 per cent, of silica, and l73/4 per cent, of
alumina; from this clay is made the delicate, translucent eggshell ware,
without the addition of any other matter. From an adjoining bluff a clay
is taken which has 50 per cent, of silica, and 38 per cent, of alumina;
from this the common porcelain is made.
Potter's clay is found in very large quantities in the provinces of
Yamashiro, Hoki, Turoo Iyo, Hizen, Higo, Owari, Mikaera, Idyn, Musashi,
and Mino. In the whole of Japan there are 283 localities where the clay
is deposited; many of these only furnish inferior clays, but they are
all fitted for use in some of the various kinds of pottery. These clays
are thoroughly powdered by means of what is called "balance pounders,"
worked in some localities by water-power, but the work is often done by
hand. The powder is then dried, and stored on boards or in flat boxes.
This dough does not go through the process of fermentation. The shaping
is almost exclusively done on the potter's wheel, which is set on a
pivot working in a porcelain eye. As a rule, the wheel is turned by the
potter himself, but in Hizen it is kept in motion by means of a band
connected with its pivot and another wheel turned by a boy. In making
dishes of other shape than round, a crude mould is sometimes used. After
the clay has been shaped on the wheel, it is set away for drying, and
usually in two or three days it is considered sufficiently dry for
smoothing, which is done on the wheel with a sharp curved knife. The
material is now made into "bisque," or biscuit, by a preliminary baking
in small ovens, when it is ready for painting, if it is to be painted
on the biscuit; if not, it is ready for the glazing. In either event it
will then go to the large furnace for the final baking. The kilns for
this purpose are always built on hill sides, and are joined together,
increasing in size from the lower to the higher ones, and in number from
four to twenty five; these kilns are so constructed that the draught is
from the lowest one, in addition to which each kiln has its own firing
place. The result of this construction is that the upper ones are by
far the most heated, and the ware is arranged accordingly; that which
requires the least baking, in the lower kiln, and that which requires
the greatest heat, in the upper. These connecting kilns have the merit
of being heat saving, but they are usually small and badly constructed,
and the heat in none of them is uniform.
The glaze is made from the silicious clay and potash extracted from wood
ashes. This potash is not a pure white, and this accounts for the dirty
color usually to be observed in unpainted Japanese ware. In different
districts the painting varies. For instance, in Owari, the greater part
of the ware is painted a cobalt blue--the cobalt ore being found in the
bluffs near the clay deposits, and is used for painting the cheaper
wares, and for this purpose German cobalt is also employed. The painting
with cobalt is generally done on the biscuit before glazing. In several
districts a very handsome ware is made, and painted on the glaze. For
this kind of painting the colors are mixed with a silicate of lead
and potash, and baked the third time in a small furnace at a low
temperature. The coloring oxides in use are those of copper, cobalt,
iron, antimony, manganese, and gold. Japanese porcelain painting may be
divided into two categories, decorative and graphic; the first is used
to improve the vessel upon which it is placed, and this class includes
all the ware except that of the province of Kaga, which would come under
the head of graphic, as it delineates all the trades, occupations,
sports, customs, and costumes of the people, as well as the scenery,
flora, and fauna of the country. "Owari ware" is made in the province
of that name; it is not as translucent, but stronger and more tenacious
than some of the Hizen manufacture.
The principal potteries are at a village called Seto, twelve miles from
the sea; in this village there are more than 200 kilns. The ware is
mostly painted a cobalt blue, and is merely of a decorative kind,
consisting of branches of trees, grass, flowers, birds, and insects, all
these being copied by the artist from nature. All the Owari ware is true
hard porcelain, and is strong and durable. In Hizen, a number of wares
are manufactured, the best known kind being the "Eurari," which is made
at Arita, but painted at Eurari. The colors in use are red, blue, green,
and gold; these are combined in various proportions, but, as a rule, the
red predominates. Generally the surface of the vessel is divided into
medallions of figures, which alternately have red, blue, or white
back-ground, with figures in green or blue and gold.
The egg-shell porcelain sold at Nagasaki is made in this province from
Arita clay, and this is made from clay with no admixture of fusible
matter except that contained by the clay naturally. The province of
Satsuma is noted for crackled ware. It is only within a very few years
that large vases have been manufactured, and in earlier days the old
ware was confined to small vessels. The glaze is a silicate of alumina
and potash, and the best ware has a complete network of the finest
crackles; the painting is of birds and flowers, and noted for its
delicate lines of green, red, and gold.
In Kioto, the ware manufactured is very similar to that produced in
Satsuma, but it is lighter and more porous; the decorations are also
nearly the same, being of birds and flowers. There is a description of
ware made in Kioto, called "Eraku," the whole body of which is covered
with a red oxide of iron, and over this mythical figures of gold are
traced. That produced in Kagja is _faience_, and in the style of
painting is unlike any other in Japan, the predominating color being
a light red, used with green and gold. The designs with which it is
profusely decorated are trees, grasses, flowers, birds, and figures of
all classes of people, with their costumes, occupations, and pastimes.
The "Banko" ware is made at the head of the Owari Bay; it is an unglazed
stone-ware, very light and durable, made on moulds in irregular shapes,
and decorated with figures in relief. On the island of Awadji, a
delicate, creamy, crackled, soft paste porcelain is made. The figures
used in decoration are birds and flowers, but outlined by heavy, dark
lines.
Consul Van Buren is of opinion that, at no distant day, Japan will be
one of the foremost competitors in the pottery markets of the world,
on account of the great variety and excellence of the clays, their
proximity to the sea, the cheapness of labor, and the beauty and
originality of the decorations. Already this important industry has been
greatly stimulated by the foreign demand, and by the success of
Japanese exhibitors at the Exhibitions of Vienna, Philadelphia, and
Paris.--_Journal of the Society of Arts_.
* * * * *
Professor Julius E. Hilgard, for twenty years assistant in charge of the
office, has been placed in temporary charge of the Coast and Geodetic
Survey. It is understood that he will be appointed superintendent to
succeed the late Captain Carlile P. Patterson.
* * * * *
THE FRENCH CRYSTAL PALACE.
The first idea of the French Crystal Palace was suggested by the English
structure of the same name at Sydenham, about eight miles from London.
Such a structure, as may be readily conceived, requires a site of vast
extent, and one that shall be easy of access and possess the most
agreeable surroundings. To the promoter of the project, those portions
of the park of St. Cloud in the vicinage of the old chateau appeared to
combine within themselves all the conditions that were desirable, and
he, therefore, on the 15th of December, 1879, addressed the Ministers of
Public Works and of Finances asking for the necessary concessions. The
extensive specifications have been finally completed and will probably
be shortly submitted for the approval of the parliament. The moment has
arrived then for the public press to take cognizance of a project which
concerns so great interests.
[Illustration: THE FRENCH CRYSTAL PALACE--PARK OF ST CLOUD, PARIS.]
At present we shall say a few words _a propos_ of the engraving we
present herewith. The French Crystal Palace will consist of one great
nave, two lateral naves, two surrounding galleries, and a vast rotunda
behind. The principal entrance, located at the head of the avenue
leading from the present ruins (which will, ere long, be transformed
into a most interesting museum), will exhibit a very striking aspect
with its monumental fountain and the dome which it is proposed to erect
over the very entrance itself. The whole structure will cover about
nineteen acres of ground, thus being two and a half times the extent of
the Palace of Industry in the Champs Elysees. The great nave of honor
will be nearly 1,650 ft. in length, 78 ft. in width, and 98 ft. in
height. The dome will measure exactly 328 ft. in height, or 105 ft. more
than the towers of Notre Dame. The structure, with the exception of
basement and foundation, will be of glass and iron.
The project which we publish to-day has been studied and gotten up,
according to the general plans and dimensions suggested by the promoter,
by Mr. Dumoulin, the architect. We are informed that the builder is to
be Mr. Alfred Hunnebelle, a contractor well known from the extensive
works that he has executed, and who is president of the Syndical Chamber
of Contractors of Paris.
Among the annexes of this palace we may note a "Palace of the Republic,"
to be built on the ruins and designed for illustrious or distinguished
visitors, such as the President of the Republic, the Ministers, the
Municipal Council of Paris, foreign delegates, etc.; a farm house for
special exhibitions and a field for experiments; galleries, cottages,
etc.
As for the programme, which embraces six divisions and numerous
subdivisions, we are unable to give it at present for want of space; we
need only say that it satisfies perfectly all the conditions of so vast
an undertaking.
In the hands of the projector, Mr. Nicole, who is well known from his
long experience in such matters, the exhibition will undoubtedly prove
a success and be instrumental in adding prosperity to all French
industries.
* * * * *
THE GREAT HEAT OF THE SUN.--Prof. S. P. Langley has made the following
calculation: A sunbeam one centimeter in section is found in the clear
sky of the Alleghany Mountains to bring to the earth in one minute
enough heat to warm one gramme of water by 1 deg. C. It would, therefore,
if concentrated upon a film of water 1/500th of a millimeter thick,
1 millimeter wide, and 10 millimeters long, raise it 83 1/3 deg. in one
second, provided all the heat could be maintained. And since the
specific heat of platinum is only 0.0032 a strip of platinum of the same
dimensions would, on a similar supposition, be warmed _in one second_ to
2,603 deg. C.--a temperature sufficient to melt it!
* * * * *
CHATEAU IN THE AEGEAN SEA.
From the site of this building, magnificent views are obtained over the
island-dotted sea and the mainland of Asia Minor: but, "though every
prospect pleases," it is a land of earthquakes, and unfortunately, the
works at the chateau have been suspended, owing to the dreadful calamity
which has recently fallen upon the district. The building is intended
for the residence of an English lady of exalted rank. It is to be built
of local white stone, the hall, staircase, etc., being lined and paved
with marbles. The hall is a large apartment about 25 ft. high, with
paneled ceiling, having galleries on two sides, giving access to the
rooms surrounding it on first floor, and to the turret staircase leading
to roofs, etc. With the exception of sanitary apparatus, painted
windows, etc. (which will be supplied by English firms), the whole of
the work will be executed by native labor. The architect is Mr. Edwin T.
Hall, London.--_Building News_.
[Illustration: SUGGESTIONS IN ARCHITECTURE--A CASTELLATED CHATEAU.]
* * * * *
ELECTRIC POWER.
Just now nothing save electricity is talked about in scientific circles.
During the meeting of the British Association the greatest possible
prominence was given to electrical questions and propositions The
success of the electric light, the introduction of the Faure battery
with a great flourish of trumpets, and the magnificent display of
electrical instruments and machinery at Paris, have all operated to the
same end. The daily press has taken the subject up, and journals which
were nothing hitherto if not political, now indulge in magnificent
rhapsodies concerning the future of electricity. Even eminent engineers,
carried away by the intoxication of the moment, have not hesitated to
say that the steam engine is doomed, and that its place will be taken by
the electricity engine. In the midst of all this noise and clamor and
blowing of personal trumpets, it is not easy to keep one's head clear,
and mistakes may be made which will cause disappointment to many and
retard the progress of electrical science. We confidently expect that
electricity will prove a potent agent by and by in the hands of the
speculator for extracting gold from the pockets of the public, and we
write now to warn our readers in time, and to endeavor to clear the air
of some of the mists with which it is obscured. There is, no doubt,
a great future before electricity; but it is equally certain that
electricity can never do many things which the half informed may be
readily made to believe it will do. We propose here to say enough
on this point to enlighten our readers, without troubling them with
perplexing problems and speculations.
No one at this moment knows what electricity is; but for our present
purpose we may regard it as a fluid, non-elastic, and without weight,
and universally diffused through the universe. To judge by recently
published statements, a large section of the reading public are taught
that this fluid is a source of power, and that it may be made to do the
work of coal. This is a delusion. So long as electricity remains in what
we may call a normal state of repose, it is inert. Before _we can get
any work out of electricity a somewhat greater amount of work must be
done upon it_. If this fundamental and most important truth be kept in
view it will not be easy to make a grave mistake in estimating the value
of any of the numerous schemes for making electricity do work which will
ere long be brought before the public. To render our meaning clearer,
we may explain that in producing the electric light, for instance, a
certain quantity of electricity passes in through one wire to the lamp,
and precisely the same quantity passes out through the other wire, and
on to the earth or return wire completing the circuit. Not only is the
quantity the same, the velocity is also unchanged. But in going through
the lamp the current has done something. It has overcome the resistance
of the carbons, heated them to a dazzling white heat, and so performed
work. In doing this the current of electricity has lost something. Led
from the first lamp to a second, it is found powerless--if the first
lamp be of sufficient size. What is it that the electricity has lost?
It has parted with what electricians would term "potential," or the
capacity for performing work. What this is precisely, or in what way the
presence or absence of potential modifies the nature of the electric
current, no one knows; but it is known that this potential can only be
conferred on electricity by doing work on the electricity in the first
instance. The analogy between electricity and a liquid like water will
now be recognized. So long as the water is at rest, it is inert. If we
pump it up to a height, we confer on it the equivalent of potential.
We can let the water fall into the buckets of an overshot wheel. Its
velocity leaving the tail race may be identical with that at which it
left the supply trough to descend on the wheel. Its quantity will be
the same. It will be in all respects unchanged, just as the current
of electricity passing through a lamp is unchanged; but it has,
nevertheless, lost something. It has parted with its potential--capacity
for doing work--and it becomes once more inert. But the duty which it
discharged in turning the mill wheel was somewhat less than the precise
equivalent of the work done in pumping it up to a level with the top of
the wheel. In the same way the electric current never can do work equal
in amount to the work done on it in endowing it with potential.
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