Geology of St. Croix. T'S 



ble, especially at a little distance below the surface. It is often 

 dug up for the purpose of deepening the soil, and left to decom- 

 pose upon the surface. The lower beds, which rarely appear on 

 the surface, are seen to good advantage along the southern coast, 

 and consist principally of coral and shells converted into a ragged 

 mass of nearly pure lime. The name coral crag^ which I have 

 applied to them, well describes their general appearance. The 

 superficial beds, which are very imperfectly. stratified, and have 

 the appearance of a chemical deposit, vary in thickness on the 

 coast from two to ten feet. The coral crag is not peculiar to St. 

 Croix. I saw extensive beds of it in Barbadoes and Jamaica, 

 where it often rises to the surface of the ground. 



The whole calcareous group, which I have now described, ob- 

 viously belongs to the tertiary formation. The first and most 

 recent division may be classed with the formation of Guadaloupe, 

 in which human skeletons have been found ; and the others I am 

 inclined to think do not extend back beyond the newer Pliocene 

 of Lyell. I do not speak with entire confidence, because nearly 

 all the shells which are found occur in the form of casts, from 

 which it is often difficult to decipher the genera and species.* 



Fossil coral, unaccompanied by marine shells, also occurs in 

 many places; sometimes beautifully colored, and incrusted with 

 calcareous depositions. Whatever may be the age of this forma- 

 tion, it is no doubt more recent than the indurated clay ; for, in 

 addition to other facts already suggested, we find imbedded in it 

 great quantities of angular fragments and even large masses of 

 rocks from that group. This circumstance may be explained on 

 the supposition that the island has been elevated at two difi^erent 

 periods ; indications of which, if I mistake not, are found at 

 several places, and especially at Jolly Hill, a distance of about a 

 mile from the west coast, and near a hundred feet above its level. 

 They consist of a calcareous deposit by the side of the road, near 

 the mill, upon the uplifted strata of the indurated clay, resembling 

 those which I have already described ; and stratified banks of 

 gravel contiguous to the garden, in which marine and lagoon 

 shells are promiscuously imbedded. On the lower grounds be- 



* The two best localities for shells are a quarry near Dr. Stednian's at the west 

 end of the island, and one at the east end, from which building stone was obtained 

 for the new prison. ' 



Vol. XXXV.— No. 1. 10 



