[ 6? ] 



from it ; hence the equinodial ftorms and frequent variations of 

 the barometer in thofe feafons. 



The quantity of asquatorial air devolved on our hemifpherc 

 in different years is variable, and fo is the quantity confumed in 

 the northern regions ; hence the mean barometrical height is dif- 

 ferent in different years. A fet of obfervations on the changes 

 that take place between the tropics in different years, compared 

 with thofe that happen in northern and intermediate regions, 

 would remove all the obfcurities that attend a minute confider- 

 ation of this fubjedt. Barometers in the middle latitudes might 

 apprife us of the quantity of air derived to our hemifphere, and 

 thofe in polar regions might inform us of the quantity con- 

 fumed ; but as thefe obfervations have not been yet made, we 

 muft content ourfelves with a general view of what appears to 

 be the principal caufe of thefe different annual variations. 



In feme years the accumulation refting on the mountainous 

 countries of the fouth of Afia and Europe, and the northern part 

 of Africa, is greater than in other years, owing perhaps to a greater 

 or earlier fall of fnow ; when this happens the northern air is 

 lighter and the fouthern colder than ufual, and fouth winds 

 principally prevail, which, in the northern parts (ufually fubjedt 

 to far greater cold) muft appear comparatively warm ; hence, 

 when the winter is remarkably fevere in the fouth of Europe 

 and Afia, it is often as remarkably mild in the northern parts, 

 and the barometer low. 



K 2 Though 



