52 Miscellaneous Geological Topics 
the vegetable soil rests upon the stratum which abounds in arenace- 
ous quartz; and that which is rendered tenaceous by alumina and 
iron is wanting. The trees which cover this land, do not exceed 
fifty or sixty years of age. This land has, in most places, a deep 
vegetable mould, but why it should be without the iron and alumina 
can be accounted for only upon the supposition, that for the greater 
part of the period of its present position, it remained a prairie. 
From this it would appear, that grass does not much contribute to 
the generation of a sub-stratum, so desirable to the farmer,—without 
which -he is but poorly compensated for his toil in collecting and 
spreading his manure upon a soil which is unable to retai, and-ap- 
propriate it to use. We therefore conclude, that this section of our 
district was a prairie for, at least, six hundred years before the cane 
got possession of it. 
It may be supposed, that the expecgbambent stratum of alee was 
the last washed down, and brought with it the properties it now ex- 
hibits. To show that such a conjecture was unfounded, we state, 
that all the sides of hills, as well as the tops of the ridges and the 
plains, are furnished with this stratum ; but whenever we approach a 
grove of aged magnolia trees, which wee usually occupies the point of 
a ridge, whether the grove is on the summit or on the side of the ridge, 
if the rain can remove the leaves, this stratum will be wanting. It 
must be remarked, that the magnolia groves so completely obscure 
the rays of the sun, as to prevent entirely the growth of the cane, or 
permit, at most, only a scattered and small growth. It has been alé 
ready stated, that this clay is. found on the sides of the hills, where 
the cane enjoyed freedom of light, and occasional access to the rays 
of the sun. ‘This fact, with the actual appearance of the furrowed 
ridges, scooped out on both sides every ten or twenty steps, will 
suffice to show that the clay was not brought froma distance and 
deposited there ; but that it was deposited fia the operation of an 
earlier cause, and that it remained notwithstanding the disadvanta 
such a situation would be attended with in — of equa 
waste from rain. 
- While upon the subject of this sub-stratum, we shall mention the 
invariable occurrence of a blue stratum of tough clay, generally 
found immediately above the sand, or within a few feet of it. When 
wells are sunk and water obtained in this clay, like that in the Lon- 
don clay, it is never fit for use; its smell and taste are very offensive 
being not unlike that of the mud of a salt marsh. In this stratum 
