128 THE PROGRESS OF PHOTOGRAPHY. 
partner, recognized the fact that it was necessary to coat 
the glass with a film of some suitable substance, in and 
on which the particles to be affected by the light might 
rest. After many experiments, he resorted to albumen, 
mixed with iodide of potassa, bromide of potassa, and 
common salt, in fixed proportions. The clear liquid was 
poured upon a glass plate, dried and heated until the al- 
bumen hardened and became insoluble. It was then sen- 
sitized by being dipped into a bath of silver nitrate; — 
after which it could be at once used, or dried and kept in 
a dark place until wanted. Such plates were developed 
in a solution of gallic acid, and jfized in the usual way’; 
but their great disadvantage lay in the fact that they re- 
quired too long exposure to make them of practical value. 
For portraiture, the daguerreotype held sway, and for 
sharp, clear beauty of detail has never been surpassed. 
An American (Maynard, of Boston) gave to the world 
collodion in the year 1847. 
The photographers of Europe were quick to seizeupon 
it as a possible coating for plates before sensitizing. 
There is considerable uncertainty as to who first sug- 
gested its use and successfully put the suggestion into 
practice—Le Gray, a Frenchman, Bingham and Scott 
Archer, Englishmen, being rival disputants for the honor. 
Tam of the opinion that Le Gray was the first one who 
actually used a collodion film and obtained upon it a pic- 
ture, which he did by a process described by him in a 
treatise published in 1849. 
To Scott Archer, however, the photographic world is 
indebted for the improvement and development of the 
collodion process, which marked in 1853 the greatest ad- 
vance since the publication of Daguerre’s method, a pro- 
cess known thereafter as the wet-plate process, which in 
a very short time practically drove daguerreotypes, calo- 
types, and all the other photo types from the field. 
The process invented by Talbot remains substantially 
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