EDWARD ELSWORTH. 127 
His process consisted in soaking a sheet of fine writing 
paper in a weak solution of common salt, and then brush- 
ing one side of it with a solution of nitrate of silver, 
Talcot discovered that paper treated in this way darkened 
very rapidly in bright sunlight. After an hour’s ex- 
posure in an ordinary camera obscura, he obtained a dis- 
tinct impression of the picture formed by the lens. He 
then fized his prints (7. e., dissolved out the silver salt 
not acted upon by the light) by washing them thor- 
oughly in water or in a solution of bromide or iodide of 
 potassa. He subsequently adopted the use of iodide of 
silver instead of the nitrate, but in all other respects his 
process was very different from that of Daguerre. 
He further discovered that, if his sensitized paper 
were brushed over with a mixture of gallic acid and sil- 
ver nitrate it was rendered much more sensitive, and the 
time of exposure correspondingly reduced. 
He called his process the Calotype process, and had it 
patented in England. His pictures were negatives, that 
is, the lights and shades were just the reverse of what 
they were in nature, the brightest part of a landscape 
being represented by black patches of reduced silver, 
while dark shadows, etc., were white. The paper, being 
semi-transparent, was made more so by the use of wax 
or some other translucent substance, and positive prints 
were made therefrom upon sensitized paper. 
Fox Talbot, therefore, made the first printing negative, 
and actually printed the first positives. 
To the translucent paper negatives of Talbot we are 
indebted for another advance, suggested by Sir John 
Herschel, viz.: the use of glass plates as a support for 
the sensitive salts of silver. But Sir John’s method of 
preparing such plates by immersing them in a bath of 
silver chloride until a film of silver had formed upon the 
surface of the glass, was not successful. 
Niepce de St. Victor, a nephew of Daguerre’s former 
Tl 
