12 Effect of Lakes on Climate 



valleys radiate. Suppose this mass to be naked, then you 

 have a certain effect ; substitute tufted forests for arid rocks, 

 and the phenomenon w^ill assume another character, at least 

 with regard to intensity. 



This is one of the twenty ways in which the clearing of 

 woods affects climates. Before putting his hand to the task 

 of arranging his predictions, the manufacturer of almanacs 

 ought, therefore, to enter into a correspondence with all the 

 wood-cutters of every country. 



In North America, the interior of the continent does not 

 enjoy, in the same latitudes, the same climate as the coasts. 

 By the influence of lakes, this difference disappears with re- 

 spect to all the points where the distance from these great 

 masses of water is not considerable. 



We must, therefore, expect that the drying up of a lake 

 will modify the climate of the neighbouring region ; and that 

 a vast inundation, arising from the unexpected rupture of a 

 barrier, will produce for a time an opposite effect. 



If any one should exclaim against me on seeing me regis- 

 ter causes, each of which, taken by itself, does not seem capa- 

 ble of producing a very great effect, my reply would be, — ^We 

 have to consider an influence as a whole, and in every case 

 the perturbations which it is our object to explain, are far 

 from being so extensive as the public supposes. 



According to Howard, the mean temperature of London 

 exceeds that of the neighbouring country, about a centigrade 

 degree (V'% F.) 



The difference between the two tempe|*atur^s is not the 

 same at all seasons. 



Eiectridty, 



We could not well avoid arranging electricity among the 

 causes which have a striking influence on climatological phe- 

 nomena. Let us go farther, and inquire whether the opera- 

 tions of man may disturb the electrical state of an entire 

 country. 



Clearing the wood from a mountain is the destruction of a 



