364 On the Theory of the Circulation of the Atmosphere. 



of fact the unanimous testimony of reliable witnesses is strongly 

 opposed to such a theory. At high elevations Humboldt found 

 icy winds from the south ; Condamine and Ulloa make mention 

 of the same; nor on the west side do we find any notice of 

 that excessive dryness or of the easterly winds which Maury 

 describes. 



The notes of Captain Betagh, written 150 years ago, so fully 

 embody the evidence of all later observers that I give them in his 

 own words, so far as they bear on the question. 



" One would expect it much hotter thereabouts [near Lima] 

 than it is, there being no proportion between the heat of this 

 climate in America and the same degree of latitude in Africa ; 

 for which there are two reasons : the one is the cool temper of the 

 air proceeding from the congealed snow on the mountains which 

 diffuses itself every way ; the other is the humidity of the vapours 

 which hang over the plains, and which are so frequent that, when 

 I came first to Lima, I often expected it would rain. These 

 vapours are not so coarse, low, and gloomy as our fogs ; nor se- 

 parated above like our summer clouds, but an exhalation between 

 both, being spread all round, as when we say the day is overcast; 

 so that sometimes a fine dew is felt upon the outward garments, 



and discerned by the eye upon the nap of the cloth The 



south-west winds blow upon the Peruvian coast all the year 

 round .... these easy gales always bear away the vapours from 

 the plains before they can rise and form a body sufficient to de- 

 scend in a shower ; but when they are carried further and higher 

 they grow more compact, and at length fall by their own weight 

 into rain." (Pinkerton's c Voyages/ vol. xiv. p. 8.) 



And Dampier some years earlier had written : — " On the coast 

 of Peru these [southerly] winds blow 140 or 150 leagues off 

 shore before you can perceive them to alter; but then as you 

 run further off so the wind will come about more easterly, and 

 at about 200 leagues distance it settles at E.S.E., which is the 

 true trade." 



But, reverting to the Atlantic, the Board of Trade Chart of 

 the coast of Brazil lends a strong sanction to the opinion that 

 the S.E. trade recurves in the western part of the ocean ; and 

 Cook and Vancouver, at different times of the year, support it 

 by their testimony with singular unanimity. The former says, 

 " On drawing near that coast [of Brazil] we met with the wind 

 more and more easterly, so that by the time we were in the lati- 

 tude of 10° S. we could make a south-easterly course good 



The 6th of October [1776], being then in the latitude of 35° 

 15' S., longitude 7° 45' W., we met with light airs and calms by 

 turns for three days successively." And the other, "On the 

 9th [June 1791] we had reached the latitude of 19° 47' S., Ion- 



