408 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 6, 



series, both horizontally stratified, rest one upon the other. My ex- 

 amination of the cuttings recently made for a railway about 200 

 miles in length between Savannah and Macon in Georgia, in a line 

 parallel to the section which I formerly observed in the bluffs of 

 the Savannah river, has confirmed the opinions before expressed by 

 me, namely, 1st, that the clays and sands containing the burr-stone 

 are eocene, as shown by casts of testacea and corals ; 2ndly, that 

 tliey overlie the calcareous eocene limestone and white marl. In 

 like manner I have found throughout Alabama that the lower ter- 

 tiary deposits in which the calcareous strata predominate are hori- 

 zontal, with a very undulating or uneven surface, and have been 

 covered by newer beds, also horizontal, of blood-red clay, silt, quartz 

 gravel, white porcelain earth, yellow ochreous clay, and white, pink 

 and yellow siliceous sands and ferruginous sandstone. Chert occurs 

 in some places in this upper deposit, which is so barren of organic 

 remains in Alabama, that I could only infer its eocene date from 

 the analogy of Georgia. The older eocene limestone and marl 

 must have had a very uneven surface, shaped into hills and valleys, 

 often bounded by steep precipices, before the incumbent clay and 

 sand, which is occasionally from 300 to 400 feet thick, was thrown 

 down. When the original inequalities had been for the most part 

 removed by the deposition of the argillaceous and sandy beds, the 

 existing ravines and valleys were excavated at the expense of both 

 formations, and hence it occasionally happens that two closely ad- 

 joining sections, each on the same level and of the same height, 

 exhibit a distinct series of horizontal beds. This diversity is exem- 

 plified in different parts of the bluff at Claiborne on the Alabama 

 river, which has become celebrated for the great number of perfect 

 fossil shells obtained from it by Messrs. Conrad and Lea. At the 

 new landing, the perpendicular precipice exhibits more than 150 

 feet of the calcareous formation, chiefly composed of white lime- 

 stone and marl, while the red clay and sand appear only at the top 

 of the cliff about twenty feet thick. But this upper formation, about 

 a mile lower down in the same bluff at Claiborne, is more than 100 

 feet thick, composed of sand and clay without fossils, a small por- 

 tion only of the calcareous beds cropping out from beneath. 



Sixthly, owing to the extent and thickness of the overlying clay 

 and sand, it is often impossible to obtain a clear section of the va- 

 rious subdivisions of the eocene white limestone of Alabama. To 

 this cause I attribute the obscurity in which the true age of the 

 nummulite limestone of Alabama has hitherto been involved. It 

 has been considered sometimes as an upper cretaceous group, some- 

 times as intermediate in age between the tertiary and secondary 

 series. After visiting Claiborne and the country on the other side 

 of the Alabama river in the fork of that river and the Tombecbee, 

 passing by Suggsville, Macon, Clarksville and Creagh's, all in Clarke 

 county, I am persuaded that the nummulite limestone is an eocene 

 rock, newer than all the beds of the well-known Claiborne bluff. 

 It is in fact more modern than the sandy deposit from which the 

 eocene shells described in the publications of Messrs. Conrad and 



