2 26 O?! the Animal Calculus. | 
Confirmation of this ; for Vv^hen the Urine does t 
not depofite its Tartar plentifully on the CaL i 
aihSy then its Surface acquires, by rowling ;i 
up and down in the Bladder, a kind of hard 
polifli; but when the Urine returns again, to 
its more rancid tartarine State, then the Cal- 
'Ctihs is covered with a new Coat 5 the laft: 
poliflied Surface, being the Partition between r 
the two Cloves, at which Surface they more 
‘cafily feparate than elfewhere. 
Experiment IX. 
I. ¥ Put into a Florence Flask full of cold | 
^ Water, a fmall round redifli Gravel Stone, , 
about ith of an Inch Diameter, and alfo a 
Piece of a very hard Calculus, and having 
fufpended the Flask over a Fire, when the 
Water boiled, Air arofe in plenty from the 
Gravel, whereby it was raifed up in the Wa- 
ter, and much agitated to and fro ; fo that it 
looked like the Nucleus of a Comet, with 
its lonq; Train of Air Bubbles arifin^ from ir. 
2. When it had boiled for an Hour and 
half, on pouring in a little more hot Water, 
it ceased to boil for a Minute, and during 
that time, no Air arofe from cither of the 
CalcnlL 3. An 
