SCIENTIFIC SUMMARY. 
255 
historical resume of the progress made towards photographing natural colours 
at the South London Photographic Society, and in the course of a discussion 
thereon, Mr. A. H. Wall, one of the Vice-Presidents of the Society, offered 
some suggestions in connection with a colour-printing process by light therein 
described. These were intended to advocate the using of negatives coloured 
by hand with transparent pigments. It has been since announced that M. 
Poiteven, of Paris, has produced photographs by a process which will probably 
bring Mr. Wall’s suggestion into practical use. M. Poiteven’s process is a very 
simple one, which, when perfected, may take a very important place in the 
arts by superseding some of the more costly, tedious, and uncertain processes 
in colour-printing now used. The paper was prepared with the sub-chloride 
of silver, and over it was brushed a solution composed of equal parts of a 
saturated solution of bichromate of potash, a saturated solution of copper, 
and a solution of chloride of potassium twenty grains to the ounce. Coloured 
engravings were used in lieu of negatives, and after the paper had been 
subjected to light in the printing frame, the print was first washed in water 
acidulated with chromic acid, then with water containing bichloride of 
mercury, then again with a weak solution of nitrate of lead. It was finally 
washed in distilled water to remove all soluble matter. Mr. G. W. Simpson 
has since announced as the result of some experiments, a process somewhat 
analogous to M. Poiteven’s. About two grains of chloride of strontium and 
five of nitrate of silver were added to an ounce of collodio-chloride of silver. 
A plate of opal glass being coated with this and dried before a fire, was 
exposed to diffused daylight until it darkened to a slate-colour. It was then 
exposed to sunlight for some hours under pieces of variously-coloured glass, 
and under plain yellowish-white glass with parts left uncovered. It was 
found to have all the colours of the glasses, was yellowish-white where it 
had been covered with the plain glass, and black where it had been left 
uncovered. 
New Photo-lithographic Process.— MM. Motay and Marechal, of Metz, 
Prance, have recently obtained a patent for a new photo-lithographic process. 
The specification states that the inventors have attained special effects by 
adding bichloride of mercury to the alkaline proto chromates, bichromates, 
and trichromates employed with gelatine. 
A Photographic Exhibition at Ghent will be opened under the auspices of 
the Belgian Government. The Commissioners undertake to provide frames 
for all specimens sent, and it is their intention to purchase a considerable 
number of the photographs exhibited, to be afterwards disposed of by lottery 
to the members of the Royal Society of Fine Arts. Mr. Ross, of Featherstone 
Buildings, Holborn, and Mr. Dallmeyer, of Bloomsbury Street, W.C., are the 
appointed agents. The collection will be opened in August. 
New Developers. — Humphrey’s Journal of Photography, published in 
America, gives the following formulae for a developer the writer strongly 
recommends as superior to the ordinary iron one : — 
Water . . . .64 ounces, 
Vinegar 
Sulphuric acid 
Albumen . 
Protosulphate of iron 
12 ounces, 
1 ounce, 
1 ounce, 
6 ounces. 
