[ 5* 8 3 
The Land mud needs be fo to its Height j and the 
Air over it, being many Degrees colder than the 
Trade- wind, will make a Refiftance in proportion to 
its fuperior Weight. How high this Refiftance may 
be, 1 cannot pretend to determine : If I require no 
more than 3 Miles from the Surface of the Sea to 
the Top of the higheft Ridge of Hills, within the 
Traft I am now fpeaking of, and to the cold Air 
above them, I think I make but a modeft Demand. 
Here, then, we have a Gale of Wind of the Breadth 
of 30 Degrees, 3 Miles high, carried with a great 
Velocity from Africa to America , a Momentum 
more than fufficient to drive the Air from America 
to us, if there be but a proper Direction. 
Were the whole Stream of the Trade-wind like a 
Mathematical Line, mere Length, without Breadth, 
and were this ftrait Line to ftrike on a fmooth 
Surface of a given Inclination, we could know its 
Direction exactly. For it is a Rule in Geometry, 
that the Angle of Reflexion is equal to the Angle of 
Incidence. Suppofc, for Example, that the Line of 
Trade-wind blew juft South-eaft, as it is faid to do, 
South of the Equator; that the Surface it ftruck 
againft ran exa&ly from South to North, as the Hills 
of ‘Peru do; and that the Point of Incidence were 
under the Equator ; in this Cafe the Angle of Inci- 
dence will be half a Right Angle, or an Angle of 
45 Degrees, and confcquently the Angle of Reflexion 
will be 45 Degrees: Now, as thefe Degrees, when 
the rcfle&ed Line fhall have run 90 Degrees in Length, 
will be equal to Degrees of a great Circle, and 
as we arc about 90 Degrees Eaft of this fuppofed 
Place of Contaft, therefore this rcfle&cd Line will, 
in 
