Analyfis of Earths and Stones. 171 

 ^thiy. ^ minute portion of magnefia in a 

 large quantity of argil! is beft feparated by 

 precipitating the whole and treating the pre- 

 cipitate with diftilled vinegar. 



Laftly, Calcareous Earth and Earytes are 

 feparated either by precipitating the barytes 

 by the Pruffian alkali, or the calcareous by a 

 cauftic fixed alkali, or by precipitating both 

 with the vitriolic acid, and evaporating the 

 folution to a frnall compafs, pouring off the 

 liquor and treating the dried precipitate with 

 500 times its weight of boiling water ; what 

 remains undiflblved is barofelenite. 



Table of the comparative hardnefs of different 

 Species of Stones, extracted chiefly from the 

 Memoirs of Stockholm^ for 1768. 



Mr. ^#/)?, the author of this Memoir de*- 

 termined the hardnefs of moft of the follow*- 

 ing ftones, by obferving the order in which 

 they were able to cut and make an impreffion 

 on each other. The firft are able to cut or 

 /cratch the fucceeding, but not vice verfa. 

 He added alfo the fpecific gravity of the fpe- 

 cimens he ufed; the firft column fhews the 

 hardnefs; the fecond, the fpecific gravity. 

 The four laft fpecies I have added from my 

 pwn pbfervation. 



Diamond 



