52 Miscellaneous Geological Topics 



the vegetable soil rests upon the stratum which abounds in arenace- 

 ous quartz ; and that which is rendered lenaceous 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 retain, 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 superincumbent stratum of clay 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 most 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 beeii al- 

 ready stated, that this clay is found on the sides of the hills, vvbere 

 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 from a distance and 

 deposited there ; but that it was deposited from the operation of an 

 earlier cause, and that it remained notwithstanding the disadvantages 

 such a situation would be attended with in consequence of frequent 

 waste from rain. 



While upon, the subject of this sub-stratum, we shall mention the 

 invariable occurrence of a blue stratum of tough cla)^, 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 



