324 
POPULAR SCIENCE REVIEW. 
ther : — hot water, G oz. ; pulverised sugar of milk, ^ oz. ; tannin, 40 grs. ; 
tincture of opium, | drm. These are added to the water in the above order. 
The sugar of milk should he dissolved and allowed to stand half an hour 
before being filtered, after which the other ingredients are to be added. 
Photo- statistics. — At a recent meeting of the French Photographic Society, 
a suggestion was made concerning the desirability of organising plans for 
obtaining authentic photographic statistics, such as the quantity of silver 
and other chemicals consumed, the number of photographers in each country, 
the value of their productions, &c., &c. 
A Cloud Diajjhrapn. — From time to time suggestions have been made for 
effecting the uniform lighting of the negatives in a lateral direction, for it is 
a recognised fact that the intensity of the light on the centre of a photo- 
gi-aph is greater than that by which the margins are produced. This, how- 
ever, is scarcely noticeable except in the case of pictures containing a very 
wide angle. In a stop or diaphragm for a landscape lens it is desirable that a 
peculiar adjustment be made, so as to reduce the intensity of the light on the 
sky of the picture, and increase in a corresponding degree that required 
on the comparatively dark foreground. A very ingenious method of effect- 
ing this was proposed by the Rev. William Read, of Manchester, and consists 
in placing the diaphragm, not at a right angle to the axis of the lens as is 
usually done, but obliquely, and in such a manner as to transmit a much 
wider pencil of light from the foregi’ound of the scene to be photographed 
than from the sky. By this contrivance the bright sky is not overdone,” 
and represented as a flat white mass, as is so commonly the case. The 
tendency to darlmess of the foreground in the photograph is also provided 
against. The perfecting this idea has of late engaged the attention of 
opticians, and it is expected that before long an improved cloud-stop on this 
principle will be an article of commerce. 
Xeiv Photographic Societg. — A photographic society has been formed in 
Bristol, under the presidency of the Bishop of Gloucester and Bristol. There 
are many clever amateur and professional photographers who reside in 
Biistol and its vicinity; hence there is no reason why the society should not 
rapidly attain a high position. 
Neio Method of Preparing Printing Surfaces. — Mr. Davies, an Edinburgh 
amateur photographer, has completed some experiments, instituted by him 
with a view to render common papers sufficiently hard on the surface to bear 
being floated on tlie sensitising solution without absorbing it. As a conse- 
quence, I. ! is now able to produce brilliant photographs on such apparently 
unsuitable surfaces as those of brown wrapping paper, the backs of handbills, 
drawing-paper, canvas, <&c. Several good photographs, some executed on 
cartridge paper, have recently been exhibited at one of the London societies, 
as an illustration of what the process is capable of doing. Tlie method of 
preparing the paper is as follows : — From four to six grains of gelatine are 
soaked in an ounce of water for an hour, and are then dissolved by the ap- 
plication of heat. While still warm, add slowly, and with constant stirring, 
from four to five drachms of a solution of white lac. The strength of the 
lac solution should be six ounces of methylate spirits of wine to one ounce 
of either white or orange lac, according to the colour of the surface to which 
it is to be applied. Tlie mixture of the gelatine and solution of lac pro- 
