rOL. XLIV.] PHILOSOPHICAL TRANSACTIONS. 281 



much about the same quantity of earth as these stones do : whereas the calculus 

 humanus, when distilled, affords but a small quantity of earth, spirit, or oil ; the 

 greatest part of it being converted into air. 



Half an oz. of one of the stones being powdered, and infused in 4 oz. of boil- 

 ing water, made it smell strongly of horse-dung, and gave it a disagreeable taste, 

 while it was hot; but, when the infusion was cold, it lost its taste and smell, and 

 the water, after standing some time, became, without being filtered, as pale and 

 clear as before; nor did the mixture of it with oil of tartar, oil of vitriol, nor 

 aquafortis, produce anv alteration in it. This experiment, being repeated several 

 times, by infusing boiling water on the same powder, was attended with the same 

 effects, though near 1 months passed between the first and last infusions. The 

 powder, after the first infusion, appeared like mud of two different colours and 

 consistencies ; the upper part being softer, and of a lighter colour, the under of 

 a dark-brown, feeling hard like sand. This difference in the colour and texture 

 of the sediment remained in all the infusions. 



A small piece of the same, and another of the largest stone, being let fall into 

 boiling water, sunk immediately, and continued at the bottom, without rising at 

 all, though the water was kept boiling a considerable time : which shows, that 

 these stones are specifically heavier than the stone found in the stomach of a horse, 

 which Mr. Watson gives an account of in the Philos. Trans. N° 475 ; and also 

 that their constituent principles are more firmly united together, than those of 

 that stone; 2 pieces of which, being let fall into water almost boiling, immediately 

 sunk, but rose again, and continued alternately rising and sinking a considerable 

 time: and, as that gentleman observes, the powder of that stone being infused in 

 boiling water, the infusion, when cold and filtered, was of a light-brown colour ; 

 whereas the colour of the water was not changed in either of the abovementioned 

 infusions ; neither did any ebullition ensue on the mixture of them with oil of 

 tartar, vitriol, &c. 



Dr. B. tried to dissolve these stones, by digesting small pieces of them in the 

 strongest acid and alkaline menstrua, viz. spirit of salt, sulphur, oil of vitriol, 

 aquafortis, and capital soap-lees, &c. and at the same time he tried the effects of 

 those menstrua on several stones, which were given him by some of his patients, 

 who voided them. They were softened by some of them, but not totally dissolved 

 by any, except the oil of vitriol and aquafortis : nor did the aquafortis cause any 

 ebullition in dissolving them, as it did in the solution of the calculus humanus, 

 which was attended with a brisk ebullition, and hissing noise, arising from the 

 eruption of the air bubbles from it : which confirms what he observed above, that 

 these stones contain but a very small quantity of air, and that their saline and 

 oily particles are so closely combined with earth, as not to be extracted without a 

 strong fire. . , , 



VOL. IX. O o 



