308 Geological Society. — Mr. Lyell on the 



is nearly parallel to the Atlantic coast, but at the distance of 1 00 or 1 50 

 geographical miles. This great feature, Mr. Lyell states, was first 

 pointed out by Maclure, but he adds that portions of the tertiary 

 formations usually cover the hypogene rocks for a certain distance 

 above the Falls, and that their outline is very irregular and sinuous. 

 On Race's Creek near Augusta, the highly inclined clay slate, con- 

 taining chloritic quartzose beds with subordinate strata much charged 

 with iron, are decomposed to the depth of many yards into clays and 

 sands which resemble so precisely a large portion of the horizontal 

 tertiary strata of the neighbouring country, that the disintegrated ma- 

 terials might be mistaken for them, if the veins of quartz which often 

 traverse the argillaceous beds at a considerable angle, did not con- 

 tinue unaltered. The only point at which Mr. Lyell saw any organic 

 remains in beds associated with these upper tertiary red strata was 

 at Richmond in Virginia, where he obtained casts of decidedly mio- 

 cene fossils j but as he observed on the Savannah river thick beds of 

 sandy-red earth beneath the burr-stone of Stony Bluff, he concludes 

 that the same mineral character may sometimes belong to the upper 

 division of the eocene group. At the rocks six miles west of Augusta, 

 the tertiary beds derived from the hypogene rocks have the appear- 

 ance of granite, and have been called gneiss by some geologists. 

 They exhibit occasionally a distinct cross-stratification, and include 

 angular masses of pure kaolin. 



Though the Savannah, in its course from Augusta to the sea, flows 

 for the greater part in a wide alluvial plain, and has a fall of less 

 than one foot in a mile, yet Mr. Lyell descended it to obtain infor- 

 mation, by means of the Bluffs, respecting the superposition of the 

 several masses, natural sections being otherwise difficult to obtain. 

 After passing cliffs of horizontal strata in which the brick-red sand 

 and loam prevail, the first exposure of a new deposit was observed 

 at Shell Bluff, forty miles below Augusta. The height of the section 

 was 120 feet, and its extent more than half a mile. The lowest ex- 

 posed strata consisted of white, highly calcareous sand, derived chiefly 

 from comminuted shells, but the beds passed upwards into a solid 

 limestone, sometimes concretionary, and containing numerous casts 

 of shells. In one place a layer of pale green clay showed the hori- 

 zontal character of the formation. The upper part of this deposit is 

 more sandy and clayey, and incloses a bed of huge oysters, Ostrea 

 Georgiana, occupying evidently the position in which they lived. 

 The total thickness of these lower strata is eighty feet. The upper 

 portion of the cliff is composed of forty feet of the red loam which 

 prevails at Aikin and Augusta, and yellow sand. Mr. Lyell did not 

 find any fossils in this deposit, but he believes that it belongs to 

 the burr-stone formation, and therefore to be an upper eocene accu- 

 mulation. At his first inspection of the casts contained in the lime- 

 stone, he inferred that they belonged to eocene species, without any 

 intermixture of cretaceous or miocene forms ; but it was not till he 

 had the advantage of Mr. Conrad's assistance that he was able to de- 

 termine the following twelve species which are well known to be cha- 

 racteristic fossils of the eocene beds of Claiborne and Alabama : — 



