PHOTO-MICROGRAPHY. 81 
After toning, the prints must be well washed and transferred to 
the fixing solution, which should be of the same strength as that used 
for fixing the negatives. ‘The prints should be allowed to remain 
in the fixing solution for ten minutes, after which they are trans- 
ferred to water where they are to be washed until perfectly freed 
from all traces of the hyposulphite. 
There are two applications of this art I wish to mention, which 
may be of great utility—I refer to the preparation of wood blocks 
for the purpose of illustrating 
microscopical work, and also 
for the production of lantern 
transparencies. The greatest 
expense in producing good illus- 
trations is that of the artist, but 
if the picture is put upon the 
wood the remainder of the work 
is cheaply and expeditiously 
performed. One way of doing 
this is to transfer an autotype 
carbon picture to the prepared 
wood block; but to produce 
good pictures upon wood it is 
better to employ the wet collo- 
dion process. 
A slightly over developed 
positive is produced upon glass 
in the ordinary way, being de- 
veloped with an iron developer 
and the film transferred to the 
~— sg woodblock in the following man- 
Fig. 8. ner. The block is first to be 
coated with a gelatine solution 
made by soaking one ounce of Nelson’s gelatine in nineteen ounces 
of water for twelve hours, dissolving with heat, and stirring in a 
solution of 20 grains of chrome alum in one ounce of water. 
When thoroughly incorporated, add sufficient lamp black to form 
an even black coating upon the wood. 
If the block be first coated it will be dry and ready to receive 
the film by the time the operator has proceeded thus far. The 
positive having been taken, developed and fixed, a piece of gum 
paper is “‘squeegeed ” to the wet film, which must then be stripped 
off the glass; the paper and film may now be trimmed with the 
scissors and brought into contact with the prepared block under 
water, gently squeegeed to remove air and water, and set aside for 
a while so that the two films may become amalgamated. After a 
short time the block is soaked in tepid water to remove the gummed 
