366 Dr. Draper on the Tithonotype, 
isinglass (p. 200 (27.) p. 201 (34.)) dried in a similar manner, 
does the same thing, and will even rend off the yellow coating 
of iodine if it has not been previously removed. 
8. Now, in addition, I have to state that if on a picture that 
has been fixed by a film of gold, so as to be irremoveable, a 
layer of isinglass be caused to dry and split up, it will bear 
on its surface a complete impression of the drawing, all the 
details being given with inexpressible beauty, the minutest 
lines and dots being present. 
9. From the same plate a series of these impressions may 
be taken. The images that are on them may be seen either 
by reflected or transmitted light, in the former instance most 
favourably by placing them on black velvet. 
10. I have hopes of improving this method so as to intro- 
duce it into effectual use. The practical difficulties that are 
in the way rest in the circumstance that the isinglass often 
splits off in chips instead of separating in one unbroken sheet. 
And the plate from which the impressions are taken, or with 
which the printing process is carrying on, becomes injured ; 
not by having its surface removed, but by the isinglass ad- 
hering in circumscribed places, and obstinately refusing to 
detach itself. 
- 11. This refinement on the art of printing, or rather of 
casting, might be supposed to give rise to very perishable re- 
sults. This however is far from the case; I have now by me 
proofs made nearly two years ago, and they do not seem to 
have undergone any change. ‘hey have lain loosely in a 
drawer. 
12. I presume, therefore, that any process which can ex- 
hibit the colours of mother-of-pearl will also exhibit Daguer- 
reotype images. This lays open a variety of new branches 
of the photographic art. 
13. As a name for these processes of copying the surface of 
a Daguerreotype, I would suggest the word TirHonotyPE. 
14, To carry this process into effect the operator proceeds 
as follows:—The Daguerreotype, which he designs to copy, 
is to be covered with a thin film of gold in‘the usual way, care 
being taken that the film is neither too thick nor too thin. If 
it be too thick the resulting copy is injured, and difficulties are 
more liable to arise in effecting the separation of the gelatinous 
coat; if too thin, the plate itself will suffer injury by having 
the figure torn off. 
15. A clear solution of isinglass is next to be prepared ; it 
must be of such a consistency that a drop of it poured ona 
cold metallic plate will speedily set. Much of the success of 
the process depends on this solution being properly made. 
