THK FLOOD OF 1843. 77 



arrests the progress of a flood downwards, and, as very fre- 

 quently happens on small plains, a causeway connects the 

 bridge with the hill on either side, the waters will accumulate, 

 and will finally burst through the least resisting part of the 

 barrier, which will most probably be the bridge. Having 

 once found a vent, the pent up waters will issue forth with a 

 velocity proportioned to the difference in the level and mass 

 of water, and a debacle will be produced whose transporting 

 power will be much greater than that of the general force of 

 the flood, if no such barrier existed. It must also be recol- 

 lected, that man by his contrivance of ditches and drains, 

 prevents the rain water from remaining the time that it would 

 otherwise do on the slopes of hills, conducting it, as he does, 

 by numerous free channels into the vallies below ; so that in 

 a given time, a much greater body of water is collected than 

 could happen in an uncultivated country." In addition to 

 this, it may be remarked, that clearing a country of timber 

 will greatly add to the velocit}^ with which a flood will pass 

 along the vallies of the streams.* 



Nothing connected with the late freshet has caused more 

 astonishment than the numerous facts which it has given rise 

 to, exhibiting the power of deep and rapid currents in trans- 

 porting materials of a higher specific gravity than water — 

 that is, materials of a greater weight than water, bulk for 

 bulk. Rocks of great weight, and materials composed chiefly 

 or wholly of iron, were in many instances transported to very 

 considerable distances from the places which they had previ- 

 ously occupied. 



In the transportation of rocks and stones in water, it must 



* It has been observed since the great freshet, that the creeks rise in 

 a much shorter time after a rain than they ditl previously. This is par- 

 ticularly the case with Chester creek. The change in this respect is 

 readily accounted for. The channel of every water course, however 

 small, has been so completely swept out, so entirely freed from obstruc- 

 tion, that the water is permitted to pass along to the large creeks in a 

 much shorter time than formerly. 



