268 TEANSPORTING POWER OF WATER. 



torrents of the Alps. In a flood of the Ottaquechee, a smaL 

 river which flows through "Woodstock, Yermont, a mill-dam on 

 that stream bm'st, and the sediment with which the pond was 

 filled, estimated after careful measm-ement at 13,000 cubic yards, 

 was carried down by the current. Between this dam and the 

 slackwater of another, four miles below it, the bed of the stream, 

 which is composed of pebbles interspersed in 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 Avidth of fifty-five or sixty feet, and, for a distance of about two 

 miles, except at two or three intervening rapids, fiUed 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 chan- 

 nel, lined with sand, and reducing the depth of water, in some 

 places, from five or six feet to fifteen or eighteen inches. Ob- 

 serving 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 conse- 

 quence of the elevation of the bed and the filhng 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 undisturbed 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 httle 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 filled, or nearly so, even this material 

 could no longer be deposited in it. The fact of the complete 



