452 



jVoies on the Influence 



[No. 36, 



2d. " That more rain falls on the sea coast than in inland dis- 

 tricts, and that, when chains of mountains run parallel to the sea shore, 

 the sides next the sea receive more rain than their opposite sides." . 



3d. That woodlands in fiat countries do not perceptibly increase 

 the quantity of rain, but that woods on mountains have a perceptible 

 influence in producing that effect." 



Monsieur Moreau de Jonnes' work is stated to have originated in 

 representations at the commencement of the French Revolution, of 

 the injurious effects on the climate, &;c. of France by the rapid cutting 

 down of forests. 



In France in 1750 the woods are stated to have occupied \ of the 

 surface of the country; in 1788, i, and in 1814 only about y^. In 

 England, according to M. Moreau de Jonnes, the woods occupy only 

 about ^ of the surface. 



There is also an interesting paper on tlie subject of climate, as af- 

 fected by the clearances of forests, in Sillinian's American Journal of 

 Science and Art, by Dr. Forry of the United States. 



" Dense Forests," he observes, " and all growing vegetables, 

 doubtless tend considerably to diminish the temperature of summer, 

 by affording evaporation from the surface of their leaves, and pre- 

 venting the calorific ray from reaching the ground." 



" Snow lies longer in forests than on plains, because in the former 

 locality, it is less exposed to the action of the sun." 



At Hudson's Bay the ground in open places thaws to the depth 

 of 4 feet, and in the woods to the\ depth of only 2 feet." 



" Moreover, it has been determined by thermometrical experi- 

 ment, that the temperature of the forest at the depth of 12 inches 

 below the surface of the earth, is, compared with the adjacent open 

 field, at least 10^ lower during the summer months, while no dif- 

 ference is observable during the season of winter." 



Lyell in his principles of geology observes, that " in the Unit- 

 ed States of N. America it is unquestionable, that the rapid clear- 

 ing of the country has rendered the winter less severe, and the 

 summer less hot ; in other words, the extreme temperature of Ja- 

 nuary and July have been observed, from year to year, to approach 

 nearer to each other : whether in this case, as in France, the mean 

 temperature has been raised seems by no means yet decided, but 

 there is no doubt that the climate has become, a§ Buffon would 

 have said, ' less excessive.' " 



