94 Prairies of Alabama. 
mixed in their composition. ‘This tract of country is from one hun- 
dred to one hundred and thirty miles wide, perhaps more. 
In speaking of the prairies, the rock formation claims particular at- 
tention. Itis uniformly found below the prairy soil, at various depths, 
ranging from ten to fifteen feet and it sometimes projects above the 
ground. ‘This rock, is generally known by the name of rotten lime- 
stone ; when removed for several feet on the top, and exposed to the 
action of the atmosphere for some time, it assumes a beautiful white 
color. In its soft state it is easily quarried, and blocks of almost any 
dimensions can be procured. It has been dressed by planes and oth- 
er instruments, and used in building chimneys; some of which have 
stood twelve or fifteen years without injury or decay. A summer’s 
seasoning is requisite to fit it for building. ‘This rock has been pen- 
etrated by boring to depths varying from one hundred to five hun- 
dred and fifty feet; after the first six or seven feet, it is of a bluish or 
grey color; but still soft, except in a few instances, where flint strata 
‘of a foot thick or more, have been met with. On perforating the 
rock, a full supply of good water, is always obtained, which uniform- 
ly flows over the top. I have heard of no constant running stream 
of water above this rock, except one in Pickens County, near the 
lower line. The superincumbent earth, is for a few feet, composed 
principally of stiff clay, of a whitish color; then comes the mould or 
soil, which is very black—in wet weather, it is extremely miry and 
stiff, and in dry, very hard and compact. 
_ Shells, such as the oyster, muscle, periwinkle, and some other 
kinds, are found in great quantities throughout almost all the prairies 
of Alabama and Mississippi; the first named being most numerous, 
mixed in every proportion with the others. ‘The oyster shells are 
perfectly similar to those now obtained, from the oyster-banks on the 
shores of the Atlantic. ‘The largest beds of shells in the open prai- 
ries, seem to occupy rather elevated, but not the highest places. They 
have probably been removed from the more elevated situations by 
torrents of rain. It may be that the lowest places never contained 
any shells; or if they did, as vegetable matter accumulates in great- 
er quantities in low situations, they may have been thus covered. In 
some instances, I believe they have been found in such places, sev- 
eral feet beneath the surface. They are not found in very large quan- 
tities in the timbered prairies; and indeed, so far as I have observed, 
wherever the shells are numerous, vegetation is not so luxuriant as 
where there is a proper admixture of the decomposed or decompo- 
sing shells and vegetable matter. 
