236 DRAINAGE OF FOREST-SOIL. 



meadow or plougliland, to delay, by their chilling influence, the 

 advent of the tardy spring. 



Another important effect of the removal of the forest shelter in 

 cold climates may be noticed here. "We have observed that the 

 gi'ound in the woods either does not freeze at all, or that if frozen 

 it is thawed by the first considerable snow-fall. On the contrary, 

 the open ground is usually still frozen when the first spring 

 freshet occurs, but is soon thawed by the warm rain and melting 

 snow. ITothing more effectually disintegrates a cohesive soil than 

 freezing and thawing, and the surface of earth which has just un- 

 dergone those processes is more subject to erosion by running 

 water than under any other circumstances. Hence more vegetable 

 mould is washed away from cultivated grounds, in such cHmates, 

 by the spring floods than by the heaviest rain at other seasons. 



In the warm climates of Southern Europe, as I have already 

 said, the functions of the forest, so far as the disposal of the water 

 of precipitation is concerned, are essentially the same at all sea- 

 sons, and are analogous to those which it performs in the Northern 

 United States in summer. Hence, in the former countries, the 

 winter floods have not the characteristics which mark them in the 

 latter, nor is the conservative influence of the woods in winter 

 relatively so important, though it is equally unquestionable. 



n the summer floods iu the United States are attended with 

 less pecuniary damage than those of the Loire and other rivers of 

 France, the Po and its tributaries in Italy, the Emme and her 

 sister torrents which devastate the valleys of Switzerland, it is 

 partly because the banks of American rivers are not yet liued with 

 towns, their shores and the bottoms which skirt them not yet cov- 

 ered with improvements whose cost is counted by millions, and, 

 consequently, a smaller amount of property is exposed to injury 

 by inundation. But the comparative exemption of the American 

 people from the terrible calamities which the overflow of rivers 

 has brought on some of the fairest portions of the Old World, is, 

 in a still greater degree, to be ascribed to the fact that, with all 

 our thoughtless improvidence, we have not yet bared all the 

 sources of our streams, not yet overthrown all the barriers which 

 nature has erected to restrain her own destructive energies. Let 

 us be wise iu time, and profit by the errors of our older brethren t 



The influence of the forest in preventing inundations has been 



