VOL. XX.] PHILOSOPHICAL TRANSACTIONS. 331 



sea, and in three at shore, greatly to my advantage, as I lost not a sail, yard, 

 or mast in two great hurricanes. 

 The causes of these hurricanes, according to experimental observations of my 



time, are these : 



1. It is known to men of experience, that to the southward of the tropics 

 there is constantly a trade-wind, or easterly wind, which goes from the north 

 to the south-east all the year round ; except where there are reversions of 

 breezes, and inlets near the land ; so that when this hurricane, or rather whirl- 

 wind, comes in opposition to the constant trade-wind, then it pours down with 

 such violence as exceeds any storms of wind. In the hurricane at Nevis, I saw 

 the high mountain that was covered with trees left in most places bare. 



2. It is remarkable by all men, that have been in those parts where the sun 

 comes to the zenith, that at his approach towards it, there is always fair weather; 

 but at his return southwards, it occasions, off the north parts of the equinoctial, 

 generally much rain and storms, as tornados, and the like; which makes the 

 wind in the tornado come on several points. But before it comes, it calms the 

 constant easterly winds : and when they are past, the easterly wind gathers force 

 again, and then the weather clears up fair. 



3. The wind being generally between the tropics and the equator easterly, 

 unless at such times as before-mentioned ; meeting with the opposition of these 

 hurricanes, which come in a contrary course to that trade-wind, causes this 

 violent whirl-wind, on the sun's leaving the zenith of Barbadoes, and these 

 adjacent islands ; by which the easterly wind lo>es much of its strength ; and 

 then the west wind, which is kept back by the power of the sun, with the 

 greater violence and force pours down on those parts where it gets vent. And 

 it is usual in sailing from Barbadoes, or those islands to the north, for a westerly 

 wind, when we begin to lose our easterly wind, to have it calm, as it is before 

 hurricanes : and then the wind springing up, till it comes to be well settled, 

 causes the weather to be various ; but after the settled westerly wind comes 

 fresh, they have been constantly without those shufflings from point to point. 



Here it is to be observed, that all hurricanes begin from the north to the 

 westward, and on those points that the easterly wind blows most violently, the 

 hurricane blows most fiercely against it; for from the N.N. E. to the E.S.E. the 

 easterly blows freshest ; sodoes the W. N. W. to the S. S. W, in the hurricane 

 blow most violent ; and when he comes back to the S. E. which is the common 

 course of the trade-wind, then it ceases of its violence, and so breaks up. Thus. 

 I take the cause of hurricanes to be the sun's leaving the zenith of those parts 

 towards the south : and secondly, the reverse or rebounding back of the wind,, 

 which is occasioned by the calming of the trade- wind. 



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