C '«7 J 
that the Air here holds not the copious Vapour It receives^ 
but lets it fall in fo frequent Rains. 
But as the cool and denfe Air , by reafbn of Its greater 
Gravity, prelTes upon the hot and rarified , 'tis demon- 
ftrative that this latter muft afcend in a continued 
ftream as faft as it Rarifies, and that being aftended, it muft 
diiperfe it felf to preferve the Mquilihrium \ that is, by a 
contrary Current, the upper Air muft move from thofe parts 
where the greateft Heat is : So by a kind of CircuIation,the 
North-Eaft Trade Wind below, will be attended with a 
South Wefterly above, and the South Eafterly with a North 
Weft Wind above ; that this is more than a bare con- 
jeOiure, the almoft inftantaneous change of the Wind to 
the oppofite Point, which is frequently found in paffing the 
limits of the Trade Winds, leems to alTure us \ but that 
which above all confirms this Hyfothefis is the Vhanomcnon 
of the Monfcons , by this means moft eafily folved, and with- 
out it hardly explicable. 
6'uppofing therefore fuch a Circulation as above, tis to be 
confidered that to the Northward of the JnAim Ocean there 
is every where Land within the uftial limit of the Latitude 
of 30. viz. Arabia. Perfia^ India &:c* which for the fame rea- 
Ibn as the Mediterranean Parts of Africa, are fubjeft to un* 
fufferable heats when the Sxxn is to the North, paffing near- 
ly Vertical ; but yet are temperate enough when the S\m 
is removed towards the other Tropicky becaufe of a ridg 
of Mountains at fbme diftance within the Land, faid to be 
frequently ih Winter covered with SnoWj over which the 
Air, as it paffes, muft needs be much chilled.Hence^it comes 
to pafi, that the Air coming according to the general Rule, 
out of the M £. in th^ Indian ifeas, is Ibmetimes hotter, 
fometimes colder, than that which by this Circulation is 
returned out of the S. W. and by confequence, fometimes 
the under Current or Wind is from the E. fometimes 
from the S. W. 
'That 
