SCIENTIFIC SUMMARY. 
675 
this ink is transferred to paper, delivered as a jelly is from its mould, the 
delicate tints, the deepest shadows, and the intermediate gradations of the 
photographic negative, are faithfully reproduced. In preparing the relievo, 
two ounces of gelatine are dissolved in six of water, and to this is added 
three-quarters of an ounce of lump sugar. Four ounces of a solution con- 
taining sixty grains of bichromate of ammonia to the ounce being added to 
this, the whole is then, while quite warm, strained. A plate of glass is next 
covered with a sheet of talc temporarily fixed by a few drops of water ; the 
talc is coated with the above, and being sensitive to light, is placed in the 
dark to set. This done, the coated talc is removed, a negative laid over the 
talc, and exposed to light in the usual way, the only change being that of 
causing the light to pass through a glass condenser and fall on it in a parallel 
direction. The hot water is then applied as above stated. In order to 
insure perfect flatness while the cast is being taken, the talc side of the film 
should be again fastened to a plate of glass with Canada balsam. Mr. 
W oodbury calculates that with three or four presses going, these mechanically 
printed photographs could be produced at the rate of 120 per hour. Apart 
from ordinary purposes, the process can be applied to glass for transparencies ; 
to china for burning in with enamel colours ; to the production, at a cheaper 
rate, of porcelain transparencies, &c., &c. At present the prints exhibited are 
said to lack clearness ; and the high relief of the extreme darks are also 
objected to. 
Actinism. — Professor Miller, the American author of a recently published 
and important work on chemistry, has been engaged in a series of experi- 
ments, demonstrating that bodies possessing an equal power of transmitting 
the luminous rays, vary considerably in their power of conveying the chemical 
rays ; a fact of no small importance to photographers. In the course of these 
experiments it was found that although water, ice, white fluor-spar, and more 
especially pure rock salt, possessed considerable diactinic power, neither these 
nor any other substances equalled in this particular rock-crystal. The 
different varieties of glass were found to transmit rays extending beyond the 
range afforded by quartz nearly one-sixth, and a plate of glass less than one- 
hundredth of an inch thick cut off these rays almost as completely as a plate 
of twenty times that thickness did. The vapour of water, although very 
impervious to the calorific rays, freely transmitted the actinic ones ; and of 
aU the liquids examined, water was fomid to be next in order to alcohol 
in its possession of diactinic power. 
The Aniline Process. — It has been suggested as a means of improving this 
process, by Mr. Carey Lea, the able American correspondent of the British 
Journal of Photography, that naphthylamine should be substituted for 
aniline. Since then Dr. Emerson J. Keynolds has published some experi- 
ments which seem to prove that Mr. Lea is right. 
The Caoutchoucotype. — This word — which sounds like a sneeze — is the not 
very attractive title given by the editor of the American Jo^mial of Photography 
— Mr. C. A. Seeley — to a new process based upon the fact, that the compound 
of rubber and sulphur may be vulcanized by light as well as by heat. The 
raw mixture is placed in a thin sheet under the negative for a certain time. 
The effect of so doing is not rendered visible until after the application of 
a solvent, such as ether, which penetrates and expands the parts not acted 
