MifcellaneaCurioja. 8 9 



But now we have had occafion to mention 

 the difference there is between the height of the 

 Mercury at one time, from the height thereof 

 at another, it may not be unacceptable to offer 

 at fbme Reafons for the (aid difference ; which, 

 at leaft to my (elf, feem to have fbme appearance 

 of Truth. Firft, Then it's undoubtedly demon- 

 ftrable, that the height of the Cylinder of Mer- 

 cury is equal to, the weight of the whole incum- 

 bent Air, and confequently that that whole is 

 lbmetimes a fifteenth more than at other times ; 

 which cannot otherwife be, but by the accefs of 

 new Matter when 'tis heavy, and its diminution 

 when 'tis light ; that Hypothecs therefore that (hews 

 how the Air fhall be encreafed or diminifhed, in 

 any particular place, will give a Reafbn for the 

 greater and leffer height of the Mercury in the 

 Barcfcofe : But to dire6t us in the choice of the 

 feveral Caufes, which may be afflgn'd for the 

 Increafe and Decreafe of the Air, 'twill not be un- 

 neceffary to enumerate fbme of the principal Ob- 

 fervations made upon the Barometer, moft where- 

 of are fufficiently known already to all thofe that 

 are curious in thefe Matters. 



" The Firft is, That in calm Weather, when the 

 Air is inclin'd to Rain, the Mercury is common- 

 ly low. 



That in ferene good fettled Weather, the 

 Mercury is generally high. 



3. That upon very great Winds, though they 

 be not accompanied with Rain, the Mercury finks 

 lowed: of all, with relation to the Point of the 

 Compafs the Wind blows upon. : 



4. That 



