280 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 25, 



plain from the older formations of the Allegany Mountains, as is 

 usual along the eastern border of the United States. This granitic 

 formation still appears at Wetumpka on the Alabama River, where 

 the lower cretaceous rocks, as I learn from Professor Brumby, rest 

 on mica schist ; but on reaching the Cahawba further west, and the 

 Warrior River at Tuscaloosa, we find the carboniferous strata con- 

 cealing the granite, and coming, as before stated, into direct contact 

 with the cretaceous rocks, which I have seen resting unconformably 

 upon the coal at the Falls at Tuscaloosa. At this junction the creta- 

 ceous group consists of beds of quartzose gravel, such as I have seen 

 intimately connected with cretaceous fossils at Montgomery on the 

 Alabama River. At Tuscaloosa the underlying gray, micaceous 

 sandstone of the coal is full of Calamites and impressions of Lepi- 

 dodendron and Sigillaria, which I beheld with no small interest, as 

 they constitute, if I mistake not, the extreme southern limit to which 

 the peculiar vegetation of the ancient carboniferous sera has yet been 

 traced, whether on the western or eastern side of the Atlantic. It 

 is due to Mr. Conrad to state, that in an outline map of the Geology 

 of Alabama made during his tour in 1833, and which he presented 

 to me in 184'2, with permission to publish any part of it, I find the 

 northern boundary of the lower cretaceous deposits in their course 

 through the States marked out with considerable approach to ac- 

 curacy. 



The several members of the carboniferous series which I have 

 seen while in company with Professor Brumby, within a distance of 

 between thirty and forty miles north-east of Tuscaloosa, consist, first, 

 of productive coal-measures, containing the usual white quartzose 

 sandstones and grits, with greenish and yellowish sandstones, some 

 of which are thinly laminated and ripple-marked, and contain Cala- 

 mites. These form the highest beds, and below them shales and 

 clays predominate with several subordinate seams of coal, from three 

 to upwards of four feet thick. Below these beds, of which I saw a 

 thickness of many hundred feet, there lies, secondly, a great deposit 

 of quartzose grit, of which millstones are sometimes made, and 

 which reminded me of our millstone-grit, and of the fundamental 

 conglomerate of the Appalachian coal-field. It passes downwards 

 into thinly laminated sandstones and dark slates of small thickness. 

 This group is succeeded (3) by fetid limestones, with chert and 

 hornstone, usually without fossils, but in some of the siliceous beds 

 of which, casts of Encrinites, Producta, Orthis and several corals 

 abound. This inferior formation, which may perhaps belong en- 

 tirely to the carboniferous series, also contains still lower down a 

 limestone charged with iron ; and an enormous mass of brown he- 

 matite appears to constitute a regular bed, and not a vein, and to 

 be destined one day, like the coal, to be a source of great mineral 

 wealth to Alabama. 



It would have been impossible for me, during my short visit, to 

 form more than a conjectural opinion respecting the structure of 

 this coal-field, still less to determine its geographical area, had not 

 these subjects been previously studied with great care and scien- 



