212 DESCRIPTION of, l^c, 



then But, if I ufe the barometer before defcribed, and examine 

 it in the morning, I find the common barometer has deceived 

 me ; for although the furface of the mercury (lands at 297 in- 

 ches, yet I obferve, that one of the indexes has been raifed 7^, 

 and the other lowered tV during the night. Hence, inftead of 

 denoting calm weather, it fhows that, the mercury having been 

 agitated, tempefluous weather is to be expedled. 



The regifter of the weather, kept from an inftrument of this 

 kind, will be much more fatisfa(ftory than thofe hitherto ufed, 

 and regifters kept at different places can be more accurately com- 

 pared with one another. 



The levity of the atmofphere, at great heights, might alfo be 

 difcovered, by fufpending this inftrument to an air-balloon. 



XII. 



