1769. ROUND THE WORLD. 243 



though very seldom, from the N. W. Tupia reported, 

 that south westerly winds prevail in October, No- 

 vember, and December, and we have no doubt of the 

 fact. When the winds are variable, they are always 

 accompanied by a swell from the S. W. or W. S. W. ; 

 there is also a swell from the same points when it is 

 calm, and the atmosphere loaded with clouds, which 

 is a sure indication that the winds are variable, or 

 westerly out at sea, for with the settled trade-wind 

 the weather is clear. 



The meeting with westerly winds, within the 

 general limits of the eastern trade, has induced some 

 navigators to suppose that they were near some large 

 track of land, of which, however, I think they are no 

 indication. 



It has been found, both by us and the Dolphin, that 

 the trade-wind, in these parts, does not extend farther 

 to the south than twenty degrees, beyond which, we 

 generally found a gale from the westward ; and it is 

 reasonable to suppose, that when these winds blow 

 strong, they will drive back the easterly wind, and 

 consequently encroach upon the limits within which 

 they constantly blow, and thus necessarily produce 

 variable winds, as either happens to prevail, and a 

 south-westerly swell. This supposition is the more 

 probable, as it is well known that the trade-winds 

 blow but faintly for some distance within their limits, 

 and therefore may be more easily stopped or repelled 

 by a wind in the contrary direction : it is also well 

 known, that the limits of the trade-winds vary not 

 only at different seasons of the year, but sometimes 

 at the same season, in different years. 



There is therefore no reason to suppose that south- 

 westerly winds, within these limits, are caused by the 

 vicinity of large tracts of land, especially as they are 

 always accompanied with a large swell, in the same 

 direction in which they blow ; and we find a much 

 greater surf beating upon the shores of the south- 

 west side of the islands that are situated just withip 



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