234 ACTION OF FORESTS ON THE PLOW OF RIVERS. 



stream, and there lets it fall in a state of minute division, and at last 

 the spoil of the mountain is used to raise the level of the plains, or 

 is carried down to the sea. 



"An instance that fell under my own observation, in 1857, will 

 serve to show something of the eroding and transporting power of 

 streams which, in these respects, fall incalculably below the torrents 

 of the Alps. In a flood of the Ottaquechee, a small river which flows 

 through Woodstock, Vermont, a mill-dam on that stream burst, and 

 the sediment with which the pond was filled, estimated after careful 

 measurement at 1 3,000 cubic yards, was carried down by the current. 

 Between this dam and the slackwater of another, four miles below, 

 the bed of the stream, which is composed of pebbles, interspersed m 

 a few places with larger stones, is about sixty-five feet wide, though, 

 at low water, the breadth of the current is considerably less. The 

 sand and fine gravel were smoothly and evenly distributed over the 

 bed to a width of fifty-five or sixty feet, and, for a distance of about 

 two miles, except at two or three intervening rapids, filled up all the 

 interstices between the stones, covering them to the depth of nine or 

 ten inches, so as to present a regularly formed concave channel, lined 

 with sand, and reducing the depth of water, in some places, from five 

 or six feet to fifteen or eighteen inches. Observing this deposit after 

 the river had subsided and become so clear that the bottom could be 

 seen, I supposed that the next flood would produce an extraordinary 

 erosion of the banks and some permanent changes in the channel of 

 the stream, in consequence of the elevation of the bed and the filling 

 up of the spaces between the stones through which formerly much 

 water had flowed ; but no such result followed. The spring freshet 

 of the next year entirely washed out the sand its predecessor had 

 left, deposited some of it in ponds and still-water reaches below, 

 carried the residue beyond the reach of observation, and left the bed 

 of the river almost precisely in its former condition, though, of 

 course, with the displacement of the pebbles which every flood 

 produces in the channels of such streams. The pond, though often 

 previously discharged by the breakage of the dam, had then been un- 

 disturbed for about twenty-five years, and its contents consisted 

 almost entirely of sand, the rapidity of the current in floods being- 

 such that it would let fall little lighter sediment, even above an 

 obstruction like a dam. The quantity I have mentioned evidently 

 bears a very inconsiderable proportion to the total erosion of the 

 stream during that period, because the wash of the banks consists 

 chiefly of fine earth rather than of sand, and after the pond was once 



