( 6o ) 
ed : And if this Motion of the Air be fuppofed to 
arifb from any ACtion of the Parts of it on one 
another, the Confequence will be the fame. For 
this reafon it feems neceffary to fhew how tbefe 
Phenomena of the Trade-Winds may be caufed, 
without the Production of any real general Motion 
of the Air weftwards. This will readily be done 
by taking in the Confideration of the diurnal Mo- 
tion of the Earth : For, let us fuppofe the Air in 
every Part to keep an equal Pace with the Earth in 
its diurnal Motion ; in which Cafe there will be no 
relative Motion of the Surface of the Earth and Air, 
and confequently no Wind ; then by the Action of 
the Sun on the Parts about the Equator, and the 
Rarefaction of the Air proceeding therefrom, let 
the Air be drawn down thither from the N. and S. 
Parts. The Parallels are each of them bigger than 
the other, as they approach to the Equator, and the 
Equator is bigger than the Tropicks, nearly in the 
Proportion of rooo to 917, and confequently their 
Difference in Circuit about 2083 Miles, and the 
Surface of the Earth at the Equator moves fo much 
fafter than the Surface of the Earth with its Air at 
the Tropicks. From which it follows, that the Air, 
as it moves from the Tropicks towards the. Equator, 
having a lefs Velocity than the Parts of the Earth 
it arrives at, will have a relative Motion contrary 
to that of the diurnal Motion of the Earth in thofe 
Parts, which being combined with the Motion to- 
wards the Equator, a N, E. W ind will be produc’d on 
this Side of the Equator, and a S.E. on the other. 
Thefe, as the Air comes nearer to the Equator, will 
become Wronger, and more and more Eafterly, and 
be 
