^2 M. Arago on the Tliermometrical State 



liams and Jefferson.) The former predominance of the west 

 winds appears to be diminishing.* The east wind, besides be- 

 coming more frequent, is by degrees, penetrating further and 

 further into the country. 



The effect of clearing, then, in the United States seems to 

 have been more moderate colds, and more moderate heats. But 

 this says nothing as to whether its mean temperature has been 

 altered. The improvement during the winter might then com- 

 pensate for the loss during the summer. It is, however, proba- 

 ble that this compensation has no existence ; for, amidst the 

 multitude of important results which M. Boussingault has col- 

 lected during his residence- in South America, there is a table of 

 observations of the mean temperatures of the equatorial zone, 

 where we observe, without exception, that the lowest numbers 

 correspond with the most wooded regions. It is, therefore, pro- 

 bable, to use an expression of Buffon'*s, that, at the same time, 

 the American climate has become less excessive^ its mean tem- 

 perature has increased. 



It may here, perhaps, be expedient to add a word or two, 

 with the vievv^ of meeting the difficulties of those naturalists who 

 refuse to recognise in the operations of human industry, in those 

 labours which, it must be admitted, scarcely penetrate the very 

 surface of our globe, a cause adequate to the production of a 

 visible change of climate. We shall here, however, attempt no- 

 thing more, than to point out some localities where, on account 

 of the favourable position of a hill in relation to the predominant 

 winds, or of some undulation in the ground, or some other cir- 

 cumstances so little remarkable that they can scarcely be noticed, 

 a superior cHmate is enjoyed. 



Middlebourg, whose latitude is nearly a degree less than that 

 of Amsterdam, ought to have a mean temperature one degree 

 greater. In truth, however, it is fully^wr degrees less. 



The town of Brussels itself has not a mean temperature so 



• If any one doubts the immense predominancy of the west winds oh the 

 'Atlantic, the following fact may be adduced as conclusive. 

 ' Taking the mean of six years, the Liverpool packets which sail from east 

 to west, that is, to New York, employ in their voyage - - - 40 days. 



The same ships occupy in returning to Liverpool - - - - 23 days. 



