HO. On the Compofition and Properties 
fufible; but ftill it was the unrivalled Scheele who difcovered 
that the urine of healthy perfons contains fuperphofphate, 
or acidulous phofphate, of lime; and who alfo indicated the 
experiment which verified his opinion, that fbpipesent of 
lime is the bafis of bone. 
Experiments have been likewife made, for the moft part 
in a rather defultory way, and moft of them by perfons but 
little practifed in chemical inquiries, which-at leaft afford 
evidence, that urinary concretions are very different, with 
refpect to the proportion of the ingredients in their compo- 
fition, and perhaps alfo in kind. M. Fourcroy, who how- 
ever *muft not. be clafled with inexperienced chemifts, I 
believe firft obtained pruffic acid by fire, and by nitric acid, 
from thefe concretions; and fhowed that they fometimes 
contain phofphate of ammoniac and of foda; which may be 
diffolved out of ‘them by water.. M. Fourcroy alfo fays, he 
found magnefia in the inteftinal calculus of a horfe; which 
calculus was a triple combination, of one part of phofphate 
of ammoniac, two parts of magnefia, and one of water, 
befides traces of animal and vegetable matter. 
Dr. Link, in a very elaborate differtation, publifhed at 
Gottingen, in 1788, on urine and calculi, concludes that 
urinary concretions confift of phofphoric acid, lime, am-. 
moniac, oil, the bafes of different kinds of gazes, together 
with the acid fublimate of Scheele, although he did not fuc- 
ceed in obtaining it. 
It is a proof of Dr. Black’s fagacity, that he fhould have » 
been able to perceive, from a few experiments, that urinary 
concretions confifted of animal matter and the earth of 
bone, before the compofition of this earth was demeninated 
by Gahn. 
_ In this hiftorical fketch it fhould be noticed, that alkaline 
fubftances, though ufed by the Greek phyficians, and after- 
wards by the alchemical phyficians, appear to have been laid 
afide by the regular practitioners, for a century or two pre- 
ceding their revival, by the famous Mrs, Stephens, in 1720, 
Her 
