THE FIR TRIBE. 



321 



moisture. This phenomenon is owing to the 

 excessive radiation of heat from bodies which 

 present a large surface in proportion to their bulk, 

 and the consequent condensation of moisture on 

 cold substances. Precisely the same effect is pro- 

 duced on the leaves of the Firs, which are therefore 

 said, though inaccurately, to attract moisture ; the 

 true state of the case being that they are reduced to 

 a low temperature by excessive radiation of heat 

 into space, and are consequently subject to a con- 

 stant deposition of moisture in the shape of clear 

 globules, which soon becoming too heavy to 

 remain suspended on the leaves, fall to the ground, 

 and, having supplied the scanty soil with a suffi- 

 ciency of nourishment for the thirsty roots, trickle 

 away in little rills. These either sink into the 

 ground, and reappear below as mineral springs, or 

 flow along the surface, continually increasing from 

 the accession of similar tributaries, and fertilizing 

 the valleys through which the very same mists had 

 previously been carried, where they had encoun- 

 tered no substances of a temperature low enough 

 to arrest their progress. 



Again, if the leaves of mountain trees grew in 

 tufts at the extremities of the boughs, and were 

 dilated like those of the trees alluded to above, thev 

 would, whenever a fall of snow occurred (and this 

 must frequently be the case) afford a convenient 

 resting place for the descending flakes, which would 

 soon accumulate, and form a mass too heavy for 

 the branches to support, and every such occur- 

 rence would spread ruin through the forest. But 

 slender as they are, and rarely or never horizontal 

 in their direction, they do not allow the snow to 

 accumulate on the extremities. Often indeed 



II. 



Y 



