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He that travels, by fea or land, towards the equl- 
noiflial, gradually acquires motion ; from it, lofes. 
But if a man were taken up from latitude 40 
(where fuppofe the earth’s furface to move 12 miles 
per minute) and immediately fet down at the equi- 
nodial, without changing the motion he had, his 
heels would be ftruck up, he would fall weftward. 
If taken up from the equi nodial, and fee down in 
latitude 40, he would fall eaftward. 
The air under the equator, and between the tro- 
pics, being conftantly heated and rarihed by the fun, 
rifes. Its place is fupplied by air from northern and 
fouthern latitudes, which coming from parts where 
the earth and air had lefs motion, and not fud- 
denly acquiring the quicker motion of the equatorial 
earth, appears an eaft wind blowing weflward, the 
earth moving from wed to eaft, and Hipping under 
the air. 
Thus, when we ride in a calm, it feems a wind 
againft us. If we ride with the wind, ahd fader, 
even that will feem a fmall wind againd us. 
The air rariiied between the tropics, and fifing, 
mud flow in the higher region north and fouth. Be- 
fore it rofe, it had acquired the greated motion the 
earth’s rotation could give it. It retains fome de- 
gree of this motion, and defeending in higher lati- 
tudes, where the earth’s motion is lefs, will appear a 
wederly wind, yet tending towards the equatorial 
parts, to fupply the vacancy occafioned by the air of 
the lower regions flowing thitherwards. 
Hence our general cold winds are about northwed, 
our fummer cold gufts the fame. 
The 
