45 



" It is under this aspect of springs, and streamlets, and rivers, we should look at 

 them while considering the local effect upon them of forests, or of the destruction of 

 these." 



Mr. Marsh says : — " With the extirpation of the forest, all is changed. At one 

 season the earth parts with its warmth by radiation to an open sky ; receives, at another, 

 an immoderate heat from the unobstructed rays of the sun. Hence the climate becomes 

 excessive, and the soil is alternately parched by the fervours of summer, and seared by 

 the rigours of winter. Bleak winds sweep unresisted over its surface, drift away the 

 snow that sheltered it from the frost, and dry up its scanty moisture. The precipitation 

 becomes as irregular as the temperature ; the melting snows and varied rains, no longer 

 absorbed by a loose and bibular vegetable mould, rush over the frozen surface, and pour 

 down the valleys seawards, instead of filling a retentive bed of absorbent earth, and stor- 

 ing up a supply of moisture to feed perennial springs. The soil is bared of its covering 

 of leaves, broken and loosened by the plough, deprived of the fibrous rootlets which held 

 it together, dried and pulverized by sun and wind, and at last exhausted by new combina- 

 tions. The face of the earth is no longer a sponge, but a dry heap ; and the floods 

 which the waters of the sky poured over it hurry swiftly along its slopes, carrying in sus- 

 pension vast quantities of earthy particles, which increase the abrading power and me- 

 chanical force of the current, and augmented by the sand and gravel of falling banks, fill 

 the beds of the streams, divert them into new channels, and obstruct their outlets. The 

 rivulets, wanting their former regularity of supply, and deprived of the protecting shade 

 of the woods, are heated, evaporated, and thus reduced in their former currents, but 

 swollen to raging torrents in autumn and spring. 



" From these causes there is a constant degradation of uplands, and a consequent 

 elevation of the beds of water-courses, and of lakes, by the deposition of the mineral and 

 vegetable matter carried down by the waters. The channels of great rivers become un- 

 navigable, their estuaries are choked up, and harbours which once sheltered large navies 

 are shoaled by dangerous sand-bars. 



" The earth, stript of its vegetable glebe, grows less and less productive, and, con- 

 sequently, less able to protect itself by weaving a new net-work of roots to bind its par- 

 ticles together, a new carpeting of turf to shield it from wind, and sun, and scouring rain. 

 Gradually, it becomes altogether barren. The washing of the soil from the mountains 

 leaves bare ridges of sterile rock, and the rich, organic mould which covered them, now 

 swept down into the low dank grounds, promotes a luxuriance of aquatic vegetation that 

 breeds fever and more insidious forms of mortal disease by its decay, and thus the earth 

 is rendered no longer fit for the habitation of man." 



Mr. Marsh also states in regard to a forest : — ■" By its interposition, as a curtain 

 between the sky and the ground, it both checks the evaporation from the earth, and me- 

 chanically intercepts a certain portion of the dew and lighter showers, which would other- 

 wise moisten the surface of the soil, and restores it to the atmosphere by exhalation. 

 "While in heavier rains the large drops which fall upon the leaves and branches are broken 

 into smaller ones, and, consequently, strike the ground with less mechanical force, or 

 are, perhaps, even dispersed into vapour without reaching it. 



" The vegetable mould, resulting from the decomposition of leaves and of wood, 

 seems as a perpetual mulch to forest soil by carpeting the ground with a spongy covering 

 which obstructs the evaporation from the mineral earth below, drinks up the rains and 

 melting snows that would otherwise flow rapidly over the surface, and perhaps be con- 

 veyed to the distant sea, and then slowly give out by evaporation, infiltration, and perco- 

 lation, the moisture thus imbibed. The roots, too, penetrate far below the superficial 

 soil, conduct water along their surface to the lower depths to which they reach, and then 

 by partially draining the superior strata, remove a certain quantity of moisture out of 

 the reach of evaporation. 



" The meteorological effects produced thus by forests resolve themselves into the 

 prolongation and consequent increase of the evaporation of water falling in the forms of 

 rain, snow and hail, effected in two distinct operations ; first, the absorption and renten- 



