MAGAZINE of science and art. 
17 
“ Tlio animal or vegetable substances are cut up, the 
pieces hung up in heated carbonic acid pis, removed, dipped 
fora short time into a bath of gelatine, dried, and plunged 
into a bath containing tanning. When removed and dried 
they arc ready for parking, and should first be covered 
with coarsely powdered bark.” —(We give this specifica¬ 
tion in the hope that some experiments may be tried 
width will demonstrate the economy and the Utility of 
this process in the bush. There is no expensive apparatus 
necessary for the process, and should it succeed it will be 
a very great boon to hundreds of residents in the interior 
who are condemned to consume salt meat. We shall be 
very glad to record the result of aiiv experiments that may 
be made by our readers, and we have very sanguine ex¬ 
pectations of a satisfactory result.) 
Tiib extraction and utilizing of the fatty matters 
contained in the water in which wool in the grease has 
been washed, would appear to he a desirable economy. 
There can be no doubt that many thousand of pounds of 
valuable fatty matter are annually wasted in this country 
in the process of wool-washing. The difficulty is to find 
a cheap method of precipitating the oily particles, and 
wo would suggest^ it as a problem to be solved by our 
practical chemists. A patent granted to Mr. H G. Yates, 
in May 28th, 1850, for this purpose, is thus described. 
44 The greasy and soapy matters contained in water in 
which wool, cotton, &e., have been cleansed, are precipi¬ 
tated by means of rock salt, sulphate of zinc, and arsenic.” 
Sulphuric Acid Barometer.— There is on exhibition 
at the Smithsonian Institute, a gigantic_ barometer, in¬ 
vented by Mr. James Green, of New York, under the 
direction of the institution. The varying pressure of the 
air is indicated by a column of sulphuric acid, instead of 
mercury, as in the old way. The mean elevation of the 
mercurial column is about thirty inches, while in this 
instrument it is about two hundred and twenty inches, or 
eighteen feet. The range is consequently proportionally 
greater, and mere minute fluctuations are rendered pre- 
ceptible. The object. of using sulphuric acid as tlie liquid 
is that at ordinary temperatures it does not give off the 
vapour, which would fill the vacuum above, or absorb the 
air. Tlie absorption of moisture is prevented, which is a 
greater desideratum in the construction of barometrical 
instruments .—America a Paper. 
New Self-Registering Minimum Thermometer.— 
It has long been a desideratum among meteorologists to 
obtain a reliable self- registering minimum thermometer. 
We are glad to perceive that this has been accomplished 
in the most satisfactory manner, by those talented 
philosophical instrument makers, Messrs. Ncgretti and 
Zambra, of London. We have inspected one of these beau¬ 
tiful instruments at Messrs. Flavclles’, in George-street, 
and would recommend all those interested in the science 
of Meteorology to make themselves acquainted vrith.it. 
The following is a description of the instrument by Dr. 
Lee, President of the British Meteorological Society, before 
the British Association, Cheltenham, August 1 ltn, 1856, 
when the Mercurial Minimum Thermometer was exhibited. 
“ This Thermometer has a bulb of very large size, con¬ 
sequently allowing a tube correspondingly large in the 
bore for that part forming the scale. On the surface of 
the Mercury enclosed in the tube is placed a small steel 
needle, pointed at both ends, which forms the index. 
This conical needle is capable of moving freely in the bore 
of the tube, and as the mercury descends therein will, of 
course, fall with it; bnt when the mercury ascends in the 
tube, the mercury w ill pass the lower pointed end of the 
needle, and rise above the same without raising or moving 
the needle. Tilts latter will, therefore, remain stationary, 
and, consequently, its upper point will indicate the lowest 
tempetature to which it has deceuded during the 12 or 24 
hoars, and will not he affected by any subsequent rise in 
temperature. To reset the thermometer for future 
observations it is necessary simply to turn it in such a 
position that the mercury and needle in the tube will flow 
into the reservoir at the top ; biit should the needle not 
freely flow with tlie mercury, it may be assisted by a 
magnet, and readily hold there until, by re-turning the 
thermometar to the upright position, the mercury flows 
back again into the tube, and, then, with the magnet the 
needlo may ho returned to the surface of tlie mercury 
ready for future observations. Dr. Leo observed, that 
one of these thermometers had been in the hands of the 
Secretary of the British Meteorological Society ; another 
at the Royal Observatory, Greenwich ; a third at Mr. E. 
J. Lowe’s Observatory, Ilighflold House ; and others had 
been used by various members of the British Meteorolo¬ 
gical Society’ all of which had acted most accurately, and 
in two imtauces 1 had corrected errors in the alchool mini- 
mums which otherwise would have passed unnoticed 
PHOTOGRAPHY. 
The Photo-Galvanic Process of Engraving. —Light 
and electricity have been put into harness by Mr. Paul 
Pretsch, lately the manager of the Imperial Austrian 
printing office*, at Vienna, aiid trained to perform the 
united functions of tlie artist, draughtsman, and engraver. 
The first steps of this photo-galvanic process are similar 
to those adopted by the glass plate photographers, The 
operator coats a glass plate with a gelatiuous solution, 
suitably prepared with chemical ingredients, sensitive to 
light. The compounds form the coating materials which 
is allowed to dry upon the glass, or other plate, which is 
coated with it. When dry the coated plate is exposed to 
the light in a copying frame in contact with the print or 
drawing which is to bo copied. After exposure the; plate 
exhibits a faint picture on the smooth surface of the 
sensitive coating, and it is washed with certain solutions, 
when the whole image comes out in a Relief, whilst tho 
tints of of the original are still maintained. __ When 
sufficiently developed this relelvo plate is dried and 
moulded. The mould is prepared for electric conduction, 
placed in the electrotype battery, producing a thin copper¬ 
plate or matrix which is used for producing the intaglio 
printing plate. With this printing process, there is no 
fear of fading as the plate impressions are in ink and the 
attention of an ordinary printer suffices to keep tho 
picture to theLt proper color. A company has been 
formed to work this process, for which a patent has been 
taken out. They announce their intention to publish 
from photographic original illustrations of the Cathedral 
Antiquities of the British Empire. — Builder. 
JMay all’s New Material. — Mr. Mayhll, the eminent 
photographer of Regent-street, has invented a new 
material for tlie reception of photographic images, which 
promises to become one of the most valuable contributions 
to tho art that has been made for some time. The pho¬ 
tographic paper used for faking likeness.has been hitherto 
of a nature to prevent the exhibition of delicacy in tho 
gradations of tones. The paper likewise is tod absorbent 
to allow of transparent colour being laid upon it with ac¬ 
curacy and delicacy. The consequence has been that 
although photographs are in great demand, they,have not 
as yet made any serious impression on the practice of first- 
rate miniature painters. True it is that many skilful 
artists have used photographs as a ground work to bo 
covered xvith colour, and in maiiy cases have produced 
admirable results, but as they wore' obliged mostly to use 
body colour instead of transparent colour, the effect was 
really to cover aigl hide the true photograph instead of 
bringing it out. Ivory, on account of its granulated sur¬ 
face, xvas not adopted for the purpose of photography. 
Mr. May all has remedied these deficiencies by the pro¬ 
duction of a new material which p ha? all the appearance 
of .ivory, without the granular surface. . Sulphurate of 
barytes is ground together with albnrncu, and then rolled 
out into slabs of tho proper size and thickness for photo¬ 
graphic pictures. 'Lite surface is then, prepared like 
ivory. A negative image can be impressid upon this sur¬ 
face with a delicacy which has hitherto bicn unattainable. 
The most shadowy tpnes are rendered xvith perfect 
accuracy. Tho smoothness of the surface admits of tho 
shading down of tints until they approach evanescence. 
The slightest fold .of a riband is. shown xvith a fulness of 
perspcectivo which could scarcely ho produced by the 
manipulation of the most skilful artist; The work of the 
painter upon such a surface is rotiiparitively easy. The 
consequence is that minatures imprinted by photography 
upon this surface can be finis-lied, off by artists with ex¬ 
treme delicacy of execution.— 1). News. 
