48 ESSAYS AND OBSERVATIONS 



ration, reduced to the quantity of an 

 ounce. This differed in no vifible man- 

 ner from the waters before evaporation, 

 except that, after Handing a little time, 

 it depofited a fmall quantity of a grayifh 

 infipid earth, which, after a very brifk 

 effervefcence, diffolved intirely in the a- 

 cid of nitre. Nothing but fuch an earth 

 remained, when the evaporation was 

 puflied to drynefs. 



E X P E R . XXXI, 



Two drachms of fhell-marle, which 

 for three years had been expofed to the 

 open air, were treated precifely in the 

 manner defcribed in the foregoing Expe- 

 riment, and in every refpe(5l with the 

 fame appearances. The marie, after di- 

 geflion, wanted half a grain of its ori- 

 ginal weight. The filtered waters fuf- 

 fered no change from the alkaline folu- 

 tion, and left, upon evaporation, a fmall 

 quantity of calcarious earth. 



Th ese two Experiments feem to contra- 

 dict the common opinion with regard to 



the 



