C 5» 3 
But if this theory was well founded, it fol- 
lowed, from analogy, that any fubftance, which 
had a greater affinity with the vitriolic acid than 
iron had, would produce the fame effedt, in fome 
degree, as lime. To determine this : 
EXPERIMENT IV. 
I took two veffels-, containing equal meafures of 
a (hong aftringent liquor, compofed of galls and 
logwood ; into one veflel I put a l'mall quantity 
of pearl affies; the other remained as a ftandard. 
Pieces of linen and cotton cloth, after maceration 
in thefe liquors, were thrown together into a ftrong 
folution of copperas ; they were foon after taken 
out, and walked in cold water; when dry, the 
pieces prepared in affies were, all of them, much 
deeper than the others. 
I made ufe of different kinds of pearl and pot- 
affies, as well as of many kinds of aftringents ; 
the affies had the lame effect., whatever aftringent 
was made uie of, and the ftrongeft alkali always 
produced the deepeft colour; and though affies, 
ufed with an aftringent, always gave a deeper black, 
than the fame aftringent without affies, yet log- 
wood, which without affies gave not fo deep a 
colour as galls with them, gave a much deeper- 
black than galls with the fame addition. 
There w'as a remarkable difference, in this cafe, 
betwixt lime and affies, in their effedt upon log- 
wood^ with lime it gave no blacknefs, but with 
affies it produced a deeper black, than any other 
aftringent I made ufe of. 
H 2 Being 
