7ii THE FLOOD OF 1 843. 



be borne in mind that their weight is greatly diminished by 

 l)eing immersed in that fluid. Very few rocks have a greater 

 specific gravity than 3, and the greater number do not much 

 exceed 2.5. The heaviest varieties of rocks will therefore be 

 deprived of one-third of their weight, and the lighter kinds 

 which are found in this county, will weigh two-fifths less in 

 water than in the air. But in regard to materials composed 

 of iron, the comparative difference in weight will be inconsid- 

 erable, as this substance is deprived of less than one-seventh 

 of its weight by immersion in water — its specific gravity 

 being from 7.6 to 7.8. 



It has been laid down " that a velocity of water equal to 

 three inches per second, is sufficient to tear up fine clay — six 

 inches per second, fine sand — twelve inches per second, fine 

 gravel — and three feet per second, stones the size of an egg." 

 It is doubtful whether results given as the above, without any 

 reference to the depth of the water, can be of any practical 

 utility ; for it certainly does appear that the power of water 

 to transport ponderous substances depends, in some degree, 

 on the depth as well as on the velocity of the current. 

 Numerous facts in support of this position might l)e referred 

 to as the result of the flood under consideration. Rocks, 

 stones, gravel, &c., are almost uniformly deposited where the 

 current of the flood became more shallow, and in very many 

 instances, apparently in the face of a current equally rapid 

 with that which brought them to the point at which they 

 rested. 



In a clear, shallow stream, with a stony bed and a mode- 

 rate velocity, we see that the water when it comes in contact 

 with each small stone, or other inequality in the bed, rises 

 over it, causing in the surface of the stream somewhat of the 

 unevenness of the bottom, and giving rise to what is usually 

 termed "ripples." Now the same thing will undoubtedly 

 take place to some extent, when the water is much deeper, 

 and the obstructions much larger. Hut will not the power of 

 the water to rise over an obstruction be diminished, in a 



