434 OBSERVATIONS Otf 



fome part (1111 remains undiflolvcd: as any per* 

 Con may fee, if he attempt the folution of a pret- 

 ty conllderable quantity of the matter of the 

 calculi in a finall vellcl. In that cafe, what remains 

 undiflblved, gathers into one place, while the 

 liquor cools. IJut a flill better tefl is to put 

 finall bits of calculus to the weight of a few 

 grains, into a copious proportion of men fir u urn, 

 and expofe it to a heat nearly equal to that ot 

 boiling water; the greater part will then'bcdif- 

 folvcd ; but there will remain a very final! por- 

 tion of a fine white matter, almort infoluble in 

 water, fpirit of wine, acids or cauilic alkali. In- 

 creufe the heat to a boiling temperature ; and 

 the fubilance which has hitherto refilled the ac- 

 tion of the iblvents, will be reduced into flakes, 

 and will almofl difappcar, but will not even yet 

 be abfolutcly diflblved. 1 have not been able 

 to procure a fuflicicnt quantity of this matter 

 for a more accurate feries of experiments. Jiut 

 1 know that a coal which is fcarce combudible 

 and not foluble in nitrous acid, remains. 



Saccharine acid produces no precipitate in a 

 nitrous folution of calculi. Hence it is plain to 

 any perfon, that thofe calculi contain no calca- 

 reous earth ; otherwife it would be inftantauc- 

 oufly deteclcd by the Saccharine acid. Buf, 

 having obferved, in the profccution of my expe- 

 riments on elective attraclions, that on the 

 addition of a third body to two already in com- 

 bination. 



