FORMATION OF TORRENTS. 3829 
clearing are already perceptible in the comparatively unvio- 
lated region of which Iam speaking. The rivers which rise 
in it flow with diminished currents in dry seasons, and with 
augmented volumes of water after heavy rains. They bring 
down larger quantities of sediment, and the increasing ob- 
structions to the navigation of the Hudson, which are extend- 
ing themselves down the channel in proportion as the fields are 
encroaching upon the forest, give good grounds for the fear of 
irreparable injury to the commerce of the important towns on 
the upper waters of that river, unless measures are taken to 
prevent the expansion of “ improvements ” which have already 
been carried beyond the demands of a wise economy. 
In the Eastern United States the general character of the 
climate, soil, and surface is such, that for the formation of very 
destructive torrents a much longer time is required than would 
be necessary in the mountainous provinces of Italy or of France. 
But the work of desolation has begun even there, and wher- 
ever a rapid mountain-slope has been stripped of wood, incipi- 
ent ravines already plough the surface, and collect the pre- 
cipitation in channels which threaten serious mischief in the 
future. There is a peculiar action of this sort on the sandy sur- 
face of pine-forests and in other soils that unite readily with 
water, which has excited the attention of geographers and 
geologists. Soils of the first kind are found in all the Eastern 
States; those of the second are more frequent in the exhausted 
counties of Maryland, where tobacco is cultivated, and in the 
more southern territories of Georgia and Alabama. In these 
localities the ravines which appear after the cutting of the forest, 
through some accidental disturbance of the surface, or, in some 
formations, through the cracking of the soil in consequence of 
great drought or heat, enlarge and extend themselves with fear- 
ful rapidity. 
In Georgia and in Alabama, Lyell saw “the beginning of the 
formation of hundreds of valleys in places where the primitive 
forest had been recently cut down.” One of these, in Georgia, 
in a soil composed of clay and sand produced by the decompo-. 
