394? Dr. Wollaston’s Analysis of 
upon it; and in the Phil. Trans, by Mr. Lane, who, among 
other simple and compound stones, gives an account of the 
comparative effects of lixivium and heat upon a few speci- 
mens of mulberry calculus (viz. No. 7, 8, 9, 10.); but 
neither of these writers attempted to ascertain the constituent 
parts. 
Though the name has been confined to such stones as, from 
their irregularly knotted surface and dark colour, bear a distant 
resemblance to that fruit, I find the species, chemically consi- 
dered, to be more extensive, comprehending also some of the 
smoothest stones we meet with; of which one in my possession 
is of a much lighter colour, so as to resemble in hue, as well 
as smoothness, the surface of a hemp-seed. From this circum- 
stance it seems not improbable, that the darkness of irregular 
stones may have arisen from blood voided in consequence of 
their roughness. 
The smooth calculus I find to consist of lime united with 
the acids of sugar and of phosphorus. The rougher specimens 
have generally some lithic acid in their interstices. 
(lb.) Caustic vegetable alkali acquires a slight tinge from a 
fragment of this kind of stone, but will not dissolve it. When 
powdered it is thereby purified from any quantity of lithic acid 
that it may contain. Phosphoric acid will then dissolve out 
the phosphorated lime, and the remainder, after being washed, 
may be decomposed by the vitriolic. The affinity of this acid 
for a certain proportion of lime is superior even to that of acid 
of sugar ; selenite is formed, and the acid of sugar may be 
crystallized, and by the form of its crystals recognized, as well 
as by every other property. It is easily soluble, occasions a 
precipitate from lime water, and from a solution of selenite, 
