On Sun Pictures. AAT 
which, however, is only adapted for copying landscapes or 
buildings ; the third is the process upon glass, by means of 
albumen or collodion,—it is the most recently discovered, 
and combining the advantages of each, it seems not unlikely, 
at no distant day, to supersede them both. I may here 
observe that collodion is a chemical compound of ether and 
gun-cotton. 
Though tolerably conversant with all the three processes 
mentioned, it is to the second only (the Calotype) to which 
I crave attention. 
The chemicals which I make use of for the production 
of views by this process are as follows :-— 
Todide of potassium, 
Bromide of ditto, 
Cyanide of ditto, | 
Nitrate of silver crystallized 
Liquid ammonia, 
Hyposulphite of soda, 
Acetic acid strong, 
Nitric acid, 
Gallic acid crystallized, 
Muriate of soda, (common salt), 
Distilled water. 
The following are also required :— 
A camera obscura with its lens, slides, and portable 
stand, 
A pressure frame for positive pictures, 
A pair of apothecaries’ scales and weights, and gra- 
duated glass measures, 
Four square japanned tin baths a little larger than 
the sheets of paper to be used, 
Two tubs for water, 
A small still for distilling water, 
