242 Proceedings of the Asiatic Society. [Nov. 
washed till all the bichromate is removed and is then rolled in with 
soft printing ink. 
This is the simplest mode of printing but in the course 
of working out the Heliotype process Mr. Edwards found that 
it was very difficult to obtain perfect contact between the nega- 
tive and the gelatine film and thus it was impossible to obtain 
the sharpest results, so he thought of preparing a tissue which 
might be printed upon just like a sheet of sensitive photographie 
paper or carbon tissue and afterwards transferred on to a zine 
plate or any other suitable surface which would stand the wear 
and tear of printing. This was a great and valuable improvement, 
but in the course of my experiments I found some difficulty in 
transferring the tissue, and as I find that with proper precau- 
tions fairly sharp results may be obtained by printing on the 
original plate, I have abandoned the use of tissue till I have more 
fully worked out the process. 
I will now briefly describe the mode of working which, after many 
trials and failures I have found most successful. 
Having well cleaned some pieces of finely ground plate glass 
such as is ordinarily used for looking-glasses, and having carefully 
levelled them. I prepare amixture composed of— 
(elatine,.......... lounce. 
Honey Soap, ...... 30 to 60 grains. 
Pani Ws ieswiee ear, £0 SLRDNS. 
Distilled water, .... 8 ounces. 
I have found 10 grains of tannin to 1 ounce of gelatine sufficient 
to render it quite insoluble, and I think even less would do; but if 
more is added, it has the effect of rendering the film insensitive to 
light. The object of adding the soap is to render the film tough 
and prevent it from becoming brittle and breaking up when dried, 
its use for this purpose was first suggested by Mr. Johnson, in 
working the autotype process, Some precautions are necessary in 
mixing the solution so that it will give an even transparent film 
when dry. I have tried many kinds of soap, but I have found that 
the honey soap exported by Coward of London, such as is commonly 
sold by the boxwallas, is the best. The soap and tannin must be 
