THE BEECH. 



331 



His certain life, that never can deceive him, 



Is full of thousand sweets, and rich content : 

 The smooth-leaved Beeches in the field receive him 

 With coolest shade, till noon-tide's heat be spent. 

 His life is neither tost in boisterous seas. 

 Or the vexatious world, or lost in slothful ease ; 

 Pleased and full blest he lives, when he his God can please." 



The grateful coolness perceptible in woods of 

 Beech, and indeed all trees which cast a deep 

 shade, is produced by the combined influence of 

 three several causes, each depending on a distinct 

 physical fact. The first, which may be said to be 

 purely mechanical, is so plain, that every one 

 must be acquainted with it : the direct rays of 

 the sun are intercepted by the foliage, and are 

 thus prevented from heating the ground and the 

 air. But how comxes it that the same effect is not 

 produced by any other kind of shelter, the roof 

 of a house or tent for instance? The latter inter- 

 cepts the sun's rays more completely, perhaps, 

 than the leafy shelter of the grove, for, however 

 thick the foliage may be, a few straggling rays 

 contrive to force a passage through. Yet the 

 fresh coolness of an over-arching Beech-grove is 

 as different as possible from the mere shelter 

 afforded by any artificial roof. 



The reason is, that, in the former case, two 

 natural operations are simultaneously going on, 

 which have the effect of cooling the air in the 

 vicinity of the foliage, and of preventing the 

 covering itself from becoming heated; whereas, 

 in the case of the artificial roof, only one of these 

 causes operates at all, and that in a very limited 

 degree. These are radiation of heat and evapora- 

 tion. All bodies possess the property of parting 

 with their heat, which is constantly proceeding 



