300 



EXPERIMENT XVIII. 



An entire calculus, of a reddish, gritty appearance, exter- 

 nally, proved to consist of ammoniaco-magnesian phosphat, 

 weighing forty-six grains one quarter, was suspended, for 

 forty-eight hours, in a mixture, consisting of four ounces of 

 distilled water, and ten drops of weak marine acid. After 

 being taken out, and dried, it was found to have lost six 

 grains three quarters. The mixture was whitish, lost its 

 acid taste, and precipitated, on the addition of a few drops 

 of fixed alkali, the ammoniaco-magnesian phosphat, under 

 that beautiful crystalline form, so accurately described by 

 Doctor WoUaston. 



We will readily conceive, how much more the loss would 

 have amounted to, in this case, in the short space of for- 

 ty-eight hours, if the menstruum had been frequently re- 

 peated, under the regular influence of human temperature. 



EXPERIMENT XIX. 



A fragment of the same species with the above, weigh- 

 ing twelve grains, was immersed, for forty-eight hours, in 

 three ounces of distilled water, without addition: tempe- 

 rature from 60 to near 100 degrees. After being taken out, 

 and dried, it was found to have lost one grain three quar- 

 ters, became so friable as to crumble, and the solution to 

 precipitate with a (cw drops of pure ammonia. This spe- 

 cies 



