RECENT DISCOVERIES IN THOTOGRArHY. 
397 
salt but also added the requisite organifier or preservative 
body, by which the pores of the film are kept sufficiently open 
to be permeated by the developing solutions afterwards to be 
applied. 
The simplicity of the method adopted is great, its efficiency is 
obvious. A collodio-bromide emulsion that has been so nearly 
adjusted in relation to the predominance of one salt over another 
as to be in moderately good working order is poured into a large 
flat dish. After a few hours, when the thick film has become set, 
a small quantity of distilled water is poured upon it and the film 
divided into squares by means of a paper-knife or silver fruit- 
knife. By thus breaking up the film and subjecting it to a few 
changes of water all the soluble matter is entirely removed, this 
removal having been facilitated by the addition of a little 
glycerine to the emulsion before it was poured out to set. The 
function of the glycerine is mechanical, not chemical. When the 
whole of the crystallisable salts are removed the film is dried, and 
is either ready for being re-dissolved immediately, or for storing 
away for future use. There appears to be no limit to its keeping 
powers, provided it be kept in a place from which light is ex- 
cluded. To render this dried pellicle ready for use it is only 
necessary that it be dissolved in a mixture of equal parts of 
ether and alcohol, adding to it a little of an alcoholic solution 
of tannin and a similar solution of soap. 
To use a collodion prepared in this or any similar way all 
that is necessary is to pour a little of it on the glass plate on 
which the negative is to be taken, allow it to dry, and either 
expose it in the camera without further preparation or place the 
plate away until it is convenient to use it. In this way it will 
be seen that photography is now reduced to a state of great 
simplicity, so far, at any rate, as the preparation of the plates 
is concerned. 
Armed with a bottle of this sensitive emulsion, a photographer 
or tourist may now visit any country with the certainty that, 
wherever he can procure glass plates cut to such sizes as he may 
require, there can he have sensitive plates — plates, too, absolutely 
identical with each other in respect of sensitiveness — unifor- 
mity being a necessary consequence of the method by which 
they are prepared. To one accustomed to the preparation of 
plates by the usual bath method, with the subsequent washings 
and preservatives, it is very difficult at first to realise the ex- 
treme simplicity of the “washed emulsion process.” In the 
simple act of pouring the collodion from a bottle on to a glass 
plate every operation is now included. The result is a plate 
capable of yielding a high-class negative, and possessing quite 
as great a degree of sensitiveness as dried collodion plates pre- 
pared by any other method. 
