1 EXPLANATION OF THE PLATES. 



April, the coafl of India in May, the ifland of Tinian by 

 the middle of June; and that it traces round the Globe, 

 the fpiral line ^vhicH I have indicated. It might be pofhble 

 to calculate the velocity, by the time employed in running 

 over thefe feveral diftances, and in reaching the other 

 points of Latitude, till it gets up with Cape Horn, from 

 which it fets in to the North, as far as Cape St. Auguftin, 

 where it meets the general Atlantic Current toward the end 

 of July. But the detail of fo many curious circumftanccs 

 would carry mc too far. 



In no one refpefl is it polfible to afcribe the general Cur- 

 rents of the Indian Ocean, which, as has been faid, fets in, 

 for fix months, to the Eaft, and fix months to the Weft, to 

 the attradion or preflure of the Sun and of the Moon, be- 

 tween the Tropics ; for thcfe Orbs move invariably in one 

 diredion, and their action is the fame at all times, within 

 the extent of that Zone to which their motion is reftri£led. 

 Befides, if their a£lion were the caufe of it, when the Sun 

 is to the North of the Line, the wefterly monfoon ought to 

 be felt on the coafts of India, as. early as the month of 

 March, for the Sun is then nearly in the Zenith of the In- 

 dian Ocean ; but it becomes not perceptible till fix weeks 

 after, that is, till the month of May. 



On the contrary, when the Sun is to the South of the 

 Line, and at the greateft dîlîance from the Indian Ocean, 

 the monfoon takes place there a little after our autumnal 

 Equinox, that is, in the month of Oftober. Hence it is 

 evident, that thefe revolutions of the Indian Ocean have 

 not their focufes under the Equator, but at the Poles ; and 

 that the revolution of the month of March, which proceeds 

 from the North by the Weft, takes fix weeks to render itfelf 



perceptible 



