216 



THE GEOLOGIST. 



States, drawn up by Dr. Morton from tlie notes of Mr. Vanusem (1828), 

 the burr-stone, sand and clay are included in one group ; but Mr. Lyell 

 infers, from the observations which he made on the Savannah river, that 

 the burr-stone is the uppermost of the two formations. In specimens of 

 that rock obtained west of Orangeburg, twenty miles from Stoudenmine 

 Creek, Mr. Lyell recognized Ostra sellceformis, a characteristic eocene 

 shell. At Aikin, sixty miles west of Orangeburg, a cutting in an 

 inclined plane on the railway has exposed a section, 160 feet thick, of earth 

 and sand of a vermillion colour, mottled clays and white quartzose sand : 

 and included in the sands as well as the clays, are remarkable masses of 

 pure white kaolin. These strata are within ten miles of the junction of 

 the tertiary series with the great hypogene region of the Alleghany or 

 Appalachian range ; and Mr. Lyell states, that they have evidently been 

 derived from the decomposition of clay slate and various granitic rocks. 

 They appear to be destitute of fossils, both at Aikin and at Augusta, 

 where they are well developed, and must in some places be 200 feet 

 thick. Three miles above Augusta, the rapids of the Savannah River 

 are due to highly inchned clay and chlorite schists, surmounted uncon- 

 formably by tertiary strata ; and Mr. Lyell states, that on all the great 

 rivers of the Atlantic border, from Maryland to Georgia, the first rapids 

 occur where the granitic and hypogene rocks meet the tertiary, and a 

 hne uniting these points, ranges nearly parallel to the Atlantic coast, at 

 the distance of 100 and sometimes 150 geographical miles. Maclure 

 first mentioned this great feature in the geology of the United States. 

 On Rae's Creek, near Augusta, the highly inchned clay slates and asso- 

 ciated beds are decomposed to the depth of many yards from the surface, 

 and the ferruginous clays and sands which have been thus produced, 

 resemble so precisely a large portion of the horizontal tertiary strata, that 

 the altered accumulations might be mistaken for them, if the quartz veins 

 did not remain unaffected. These decomposed materials throw much 

 light, Mr. Lyell says, on the origin of the beds of red and mottled clay, 

 and of the sands usually devoid of fossils, spread extensively over the 

 low lands, and constituting the higher portions of the tertiary series. 

 The only point at which he has seen casts of shells in beds, associated 

 with the red earth, is at Richmond, in Virginia, and they belonged to 

 miocene species ; but, as at Stoney Bluff, on the Savannah, similar red 

 strata occur beneath the burr-stone, he is of opinion, that the same 

 mineral character belongs to the upper division of the eocene group. 



For the purpose of ascertaining the order of super-position of the 

 masses of strata, Mr. Lyell descended the river from Augusta to Savan- 



