126 THE PROGRESS OF PHOTOGRAPHY. 
done in a box made for the purpose, in which the pol- 
ished plate was exposed to the vapor of iodine. 
Third—The third operation was the exposure of the 
plate thus sensitized in the camera box—time of ex- 
posure from three to thirty minutes. 
Fourth—The fourth operation was the delicate one of 
development of the image by exposing the plate to the 
vapor of mercury, which also had to be done ina special 
box, wherein the mercury was vaporized by means of a 
spirit lamp; the temperature carefully regulated, and 
the development of the picture watched through a small 
glass window. 
Fifth—The last operation was the fixing in hyposul- 
phite of soda and washing in clean, hot water. 
In 1840, a Mr. Goddard of London, and in 1841 M. 
Claudet of Paris, discovered that the vapor of bromine 
and chlorine, respectively adding to the iodide of silver 
a deposit of bromide or chloride of silver, each rendered 
the plates much more sensitive to the action of light, re- 
ducing the time of exposure from thirty minutes to less 
than one minute. With these discoveries, the daguerreo- 
type seems to have reached its perfection. The period of 
its utility covered about ten years. 
I have called the discovery of Daguerre the birth of 
photography, but we must not lose sight of the fact that, 
at the very period when Daguerre and Niepce were pur- 
suing their experimental work, another man, an English- 
man, following the lines long before indicated by Wedg- 
wood and Davy, was developing a process for securing 
the fickle image of the camera obscura, and had actually 
succeeded when the proclamation of Daguerre’s success 
was made. It is quite probable, or I may say certain, 
that but for the lucky accident which disclosed the se- 
cret of developing the latent image on Daguerre’s sil- 
vered plates, Fox Talbot would be Known to-day as the 
father of photography. 
76 
