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^provision made for evaporation from the forest. There are similar stomates on every 

 verdant plant on the dry land; but the evaporating surface supplied by the leaves, rising 

 tier above tier, far exceeds in extent that supplied by the herbage and the grass growing 

 •elsewhere; and in many places these may be found growing as luxuriantly on the soil of 

 the forest as in the fields beyond, or perhaps more so, and adding their quota of evapo- 

 ration to the evaporation from the trees. " 



" Of the moisture thus raised by the tree, and no longer required when the sap has 

 been elaborated in the leaf, the air will only take up what quantity it can, at the tempera- 

 ture at that time and place, dissolve and hold in solution; and cases have been cited in 

 which the excess is so great that the leaves seem to act as alembics, distilling water which 

 falls in great drops to the ground. 



"Where this does not take place, what the air dissolves it will hold in solution so 

 long as the temperature is maintained at the same or a higher point; but if the tempera- 

 ture fall below the point at which it can do this, what it cannot sustain as invisible 

 vapour, will be deposited or suspended in the form of mist, or cloud ; and such a reduc- 

 tion may follow the setting of the sun, or even the decline of it in the afternoon and 

 towards nightfall; or if there come over the trees a wind in any degree colder than the 

 mr in which they are enveloped, the air is thereby cooled down, and a quantity of the 

 moisture which it held in solution may be deposited in the form of fog, or of dew, or of 

 rain. " 



The same writer shows us another remarkable effect of the soil of forests : — 



" A distinction has been drawn between the effects produced on the ground by the 

 «hade from sunshine, and by the shelter from drying winds afforded by trees and forests. 

 It is necessary further to distinguish between the effects produced by shade and by 

 vegetable mould, which exists always in greater or less quantity in forest soil, in conse- 

 •quence of the decay and decomposition of fallen leaves and fallen twigs, and broken or 

 decaying rootlets. 



" In the soil of a forest there generally exists more moisture than can be attributed 

 to shade, or to shade and shelter combined ; and much of this is attributable to the attrac- 

 tion of moisture manifested by this vegetable mould. 



" In this effect of vegetable mould we see how forests may exercise a third influence, 

 over and above and distinct from both shade and shelter, in maintaining a humidity of 

 soil." 



From what has been so far stated concerning the forest, my readers will have seen 

 that it is a great storehouse of moisture, so long as its natural bed and foundation be pre- 

 served from the injuries occasioned by cattle and running fires, and while it is reserved in 

 sections of sufficient depth and width, to thoroughly maintain its forest character, and 

 establish decided variations between its temperature and that of the cleared land. They 

 will have seen that that moisture will in such case be continually renewed from €he 

 depths of the earth to which the tap-roots pierce, in addition to the larger supply received 

 from the clouds above. They will ha^ e seen that the sun's rays cannot again carry off 

 this moisture when it is once within the forest wall. They will have seen that the wind, 

 which dries faster than the sun, and extremely fast when it has the sun to help it, cannot 

 dry the land in the forest. That the moisture thus kept in the forest is used to feed the 

 rivers, streams, creeks, and springs, and to keep up the whole underground system of 

 water below the fields ; and also, and in very great part, to carry up nourishment from 

 the roots to the leaves, escaping in vast volume thence to the higher atmosphere through 

 the not innumerable altogether, for they have been counted ; but through the wondrously 

 numerous openings in the leaves (160,000 sometimes to the square inch; the most 



