PHYSICAL AND LITERARY. i8i 



exceffive loudnefs of the noife, will confix 

 der, that it is not a large quantity of motion 

 communicated to the air, but rather a fmart 

 ftroke which produces found, and that the ex- 

 plofion of but a few particles of fixed air may 

 be capable of caufing. a loud noife, provided 

 they all recover their fpring fuddenly, and ia 

 the fame inftant. ..j,.j 



The above experiments lead us alfo to, 

 conclude, that volatile alkalis, and the com- 

 mon abforbent earths, which lofe their air 

 by being joined to acids, but fhew evident 

 figns of their having recovered it, when fe- 

 parated from them by alkalis, received it from 

 thefe alkalis which loft it in the inftant of 

 their joining with the acid. 



The following are a few experiments upon 

 three of the abforbent earths, made in order 

 to compare them with one another, and with 

 magnejia. 



Sufpedting that magnejia might poflibly be 

 no other than a common calcarious earth, 

 which had changed its nature, by having been 

 previoufly combined with an acid, I fatura- 

 ted a fmail quantity of chalk with the muria- 

 tic acid, feparated the acid from it again by 



means 



