RIVER SYSTEMS OF NEW HAMPSHIRE. 321 



larger amount of rain and snow is collected here than upon the same 

 area in any other part of New Hampshire.* This is effected by the 

 refrigeration of currents of air, coming in contact with the relatively cool 

 mountain ridges, their moisture being thereby condensed and precipitated 

 as rain. The clustered arrangement of our mountains and their disposi- 

 tion in numerous short ranges, transverse to the direction of our pre- 

 vailing storms, would tend to increase their influence in this respect. 



The third consideration to be noticed is, that this whole area is heavily 

 wooded, with the small exception of such alpine summits as have an 

 elevation more than 4000 feet above the sea. This condition prevents 

 the very rapid drainage which would otherwise produce overwhelming 

 freshets, sweeping all before them, after which the streams would dwindle 

 to mere rills, worthless for water-power. By this clothing of forest, 

 however, the large rainfall of this area is stored up, as in a sponge, and 

 gradually given forth, producing in our mountain-fed streams one of the 

 principal resources of our water-power when most needed in the drouth 

 of summer. This effect of forests is due to several causes. A great 

 amount of decaying vegetable materials and mosses, which become 

 saturated with rain, everywhere covers the ground in our forests, and the 

 earth is loosened through which tree roots have forced their passage, 

 giving water a chance to penetrate it, from both which conditions its 

 volume, when in surplus, is husbanded against too sudden removal. Thus 

 the forest acts as a capacious reservoir for retaining the water as it falls. 

 A further office is the protection of the ground from the parching heat 

 of the sun, and from the similar effect of drying winds, producing a 

 permanence and constancy in the springs on which the summer volume 

 of our streams mainly depends. Forests also check the waste of winter 

 snow as well as of summer rain. Patches of ice and snow may be found, 

 as late as early June, lying here and there in the defiles and ravines of 

 our northern woods, and even late in summer in secluded mountain 

 glens, saturating the ground as they melt, and sending off streamlets to 

 the nearest brook or river. It will be seen that our forests are, to an 

 important extent, so situated as to exercise their characteristic influence 



* The rainfall at the summit of Mt. Washington during the first year of observation was 55 inches, against an 

 average annual rainfall varying from 35 to 46 inches in other portions of the state (p. 13s). 



VOL. I. 43 



