274i NOTICES OF AUTHORS. 



throw out a greater continuation of shoot than the 

 under branches; nearly the whole nomishment from 

 the soil being on this account draTO up and con- 

 sumed by these top shoots, and the lower over- 

 shadowed tmgs and branches languishing and dying 

 from the absence of these advantages. Besides this 

 extension of top shoots, by the greater continuation 

 of leaves, or links of life, occasioned by the above 

 causes, these shoots, o^ving to the moist atmosphere 

 of the wood, also push out into longer spaces be- 

 tween the leaves. However, these top branches do 

 not push sun-ward, but merely in opposition to gra- 

 vity. 



Sir Henry states, that " trees certainly possess 

 some heat, otherwise they would be killed dming 

 severe frosts." Our belief of the vital heat of vege- 

 tables is placed on a much better foundation than 



mer ; and tbat nearer the equator, forests are generally cooler 

 than bare country. But the temperature is regulated so much 

 by the position of seas and lakes, in combination with the prevail- 

 ing currents and strength of currents of the air — by the configu- 

 ration of the country, — moisture and cloudiness of the atnoosphere 

 and quantity of rain, — by the composition, aiTangement, and co- 

 lour of the soil, — by the lower vegetable cover, and even by the 

 nature of the forest itself, whether deciduous or evergreen, that 

 particular facts must be very carefully weighed to enable us to 

 reach general conclusions. It is generally understood, that forests 

 render the climate moister. 



