DILUVIAL DEPOSITES. 
131 
a powerful current of water swept over the surface 
of the earth. Professor Hitchcock remarks, that 
*' in an agricultural point of view it is the least in- 
teresting of ail our strata ; for, of all the soils, it is 
the most unfriendly to rich vegetation ; and as it is 
spread, in a good measure, over every kind of rock, 
it often prevents the formation of a good soil from 
the decomposition of the rock. It is, in general, 
easily recognised in the "most steril places, in the 
form of low, rounded hills, composed almost en- 
tirely of coarse pebbles or cobble stones, and some- 
times larger rounded masses of rocks called bowl- 
ders, mixe'd with coarse sand and covered with a 
stinted vegetation. It was evidently deposited by 
currents rushing violently over the surface, since 
only the coarser materials which were driven along 
were left, w^hile the finer particles were kept sus- 
pended by the agitation of the waters. Some va- 
rieties of this diluvium may indeed be oonverted 
into a soil of tolerable richness, by manuring it 
abundantly and clearing away the stones. And 
generally, too, the rains that have fallen on it for 
thousands of years have conveyed its finer parti- 
cles to the bottom of the valleys and cavities with 
which this formation abounds ; and these being 
mixed with much vegetable decayed matter, a soil 
of good quality is formed. But these fertile spots 
ought rather to be denominated alluvium than dilu- 
Mr. Lyell, however, refers diluvial as well as al- 
luvial deposites to the action of causes now in op- 
eration ; but he acknowledges that his theory re- 
quires " thousands of centuries" to account for the 
present appearances on the surface of the earth. 
As such a deposite, however, might have been pro- 
duced by a general deluge, and as there are no facts 
in geology which render such a catastrophe improb- 
able, and we are, moreover, expressly told in scrip- 
ture that such an inundation did happen at the time 
