35© Dr. Perchal on the Purfuits 



miftry, renewed the experiments which Df* 

 Hales had begun, and found that the folvcnt 

 power, afcribed to the fermenting mixtures, 

 refided only in the fixed air: Hearing feme very 

 imperfed: accounts of this difcovery, curiofity 

 and humanity engaged me in the purfuit of it. 

 I recolledled that Dr. Black and Mr. Cavendifh 

 had proved the folubility of various earthly 

 bodies in water, either by abftrading from, or 

 fuperadding to the fixed air, which they contain. 

 And as the human calculus is dilTolved in the 

 former way, by lime water and the cauftic alkali, 

 it appeared to me highly probable, that the 

 cfFcdt would be produced, in the lame fubftance, 

 by the latter mode of operation. Analogy feemed 

 favourable to the hypothefis, and a feries of 

 experiments, which i made with great care, 

 in the fullcft manner confirmed it. Two years 

 afterwards, Dr, Falconer engaged in the lame 

 enquiry i and the refu'.ts of his trials exactly 

 coincide with thofe which I have related. This 

 united evidence has been alfo ftrengthened 

 by the fubfequent teftimony of Dr. Prieftley and 

 Dr. Hulme. Yet decifive as it appears to be, 

 a friend of mine, who is a very able and accurate 

 experimenter, alTures me, that the calculi, which 

 he has tried, uniformly refill the adlion of me- 

 phitic water. And he further adds, that not one 

 of them has been found to contain a fingle grain 

 of abforben; earth i but that all of them proved 



inflam- 



