394 Rogers's Account of two Remarkable 
far will seem more than probable if we pause and consider the 
conditions of their motion. The suspended blocks, losing, as 
we know, more than two-fifths of their weight from the buoy- 
ancy imparted by the fluid, would be carried onward a great 
distance before they could descend through several hundred 
feet of water; and after they had struck, it is very obvious 
that many of them would maintain a rapid progress for some 
distance further, bounding and rolling forward upon a floor of 
loose detrital matter moving in the same direction, and still 
impelled by the pressure of the onward current. Upon these 
considerations we may understand why the blocks, in retain- 
ing their original angular or fragmentary shape, should ex- 
hibit partial traces of abrasion at their edges, and why they 
should rest imbedded in the rounded drift to so small a depth. 
But there is a much more efficient power exerted by cur- 
rents, and precisely such as would be exercised by a great and 
rapid inundation sweeping over an irregular surface of plain 
and mountain. We here refer to the lifting or buoyant power 
of the great whirlpools or gyratory funnels, which the inequali- 
ties in the velocity of the current, produced by the local ob- 
structions in its bed, would infallibly engender. When the 
true nature and stupendous energy of this mode of fluid mo- 
tion are duly contemplated, and its special agency in the 
general inundation fitly considered, it will account, we think 
for all the previously unexplained features of the boulder 
trains, including the perplexing phenomena of their great 
length and extreme narrowness. 
We cannot in this paper assign ourselves sufficient space to 
discuss critically the dynamics of gyratory fluid motion; but 
the attentive reader will be satisfied, from the close analogy of 
such vortices in rushing water, to those terrific whirls which 
arise in the more attenuated fluid of the atmosphere, under 
the forms of the tornado and the waterspout, that their func- 
tions are strictly identical. Nothing in the natural history of 
tain has been violently ploughed off; precisely as if by the concussion of som? 
huge solid body moving with irresistible momen 
