PHOTOGEArHY AND SOME OF ITS APPLICATIONS. 625 
of tlie sitter, upon a plate of glass coated with sensitized 
collodion. This he can do in a few minutes ; and then, by 
means of his negative, used somewhat in the same manner as 
the fern-frond of which we have spoken, he prints off as many 
positives on paper as he pleases. 
The reader is now, we trust, in a position to follow us in 
our description of some of the more remarkable applications 
of photography to the arts, fine arts, and sciences. If it has 
seemed to those skilled in the profession of photography that 
we have dwelt too much upon merely rudimentary details, we 
would ask them to remember that there are others to whom 
our remarks are necessary, in order to render what we are 
about to describe intelligible. Foremost among the branches 
of industry in which photography has been employed wfith 
advantage, must be mentioned lithography. The discovery of 
a means of applying the photograph to the stone, and thus 
of working off copies of sun-pictures in ink, and that, 
too, with all the velocity which steam-power can achieve, is 
indeed a grand one. The credit of making it is claimed by 
two or three individuals, between whom it is all the more 
difficult to decide, because of some trifling differences in the 
processes they employ. Thus one candidate has termed his 
method photo-zincography, a name which is truly anything but 
euphonious, whilst the others simply use the expression photo- 
lithography, to designate a combination of the stone and sun- 
light in the operation of printing. The methods by which the 
photograph is applied to the stone are by no means complex 
ones. The mode employed on the Continent, especially in 
Austria, is as follows : — A special solution of sensitized collo- 
dion is poured upon a patent plate, and after exposure in the 
camera for a suitable time, is converted into a negative. For 
protection, the picture is then coated with a solution of gutta- 
percha, and the solution allowed to dry ; after ten or fifteen 
minutes it is again coated, but this time with a solution of 
gelatine. The next stage consists in removing the film con- 
taining the picture from the plate on which it rests ; this is 
done by pasting on thin slips of paper to the four margins of 
the picture, and then, after the picture has been moistened 
and the edges separated with a knife, by carefully peeling off 
the entire surface. Next, it is cautiously dried on a smooth 
surface, and is then ready for the stone. The latter has also 
to be prepared. Having been properly ground down, it is 
removed to a dark room and then receives a coating of a solu- 
tion of asphalt in chloroform, which, when dry, presents a 
sensitized surface. Upon this the negative film is now placed 
and firmly pressed, and then, after being covered with a patent 
plate, the whole is exposed to the sun-light for about two or 
