80 Geology of Antigua. 



hood of St. John's and of Constitution hill. Near St. John's they 

 have been disturbed by uplifting forces, and constitute two or 

 three summits of moderate elevation, on one of which stands the 

 cathedral. 



At this place, the chert is strangely intermingled with lime- 

 stone, and it is not very obvious which occupies the lowest posi- 

 tion. At an eminence a little south of this, it is broken up into 

 immense masses, which appear like outliers or ledges on the 

 sides of the hill. In the region of Constitution hill, and farther 

 south on the road to English Harbor, it appears in the form of 

 square and angular blocks, from a few inches to two feet in diam- 

 eter, strewed in great quantities over the surface of the country. 

 I saw only one or two beds which had not been disturbed. They 

 were distinctly stratified, and lay in a position, so far as I could 

 judge, conformable with the strata of the clay formation. I saw 

 no place, however, where one distinctly graduated into the other, 

 or where they came directly in contact. 



The aspect of this rock is various ; generally, however, highly 

 vitreous. It sometimes approaches to jasper, both in constitution 

 and color ; at others it is a pale hornstone ; and it is often seen of 

 a still coarser structure. The fracture is sometimes even, often 

 conchoidal, and not unfrequently splintery. The structure of 

 the masses of which I spoke on the eminence south of the 

 church, differs from any which I saw elsewhere. It was more 

 porous, giving to the rocks an appearance not unlike a silicious 

 tufa, which had been impregnated with iron and hardened by 

 heat. This family of rocks is altogether of an interesting char- 

 acter, entirely unlike any thing which I have seen in other parts 

 of the West Indies or of the world. Their geological interest is 

 greatly^increased by the immense quantities of shells which they 

 contain, supposed by Dr. Nicholson to be Melanias.* These shells 

 are always silicified ; sometimes standing out from the rock in 

 beautiful relief; at others entirely imbedded, and, with the ex- 

 ception of the coloring matter, converted into its substance. I 

 saw specimens of this description most elegantly polished. Ac- 

 cording to the best information which I could obtain, these shells 



* Dr. Nugent calls these shells cerithium. I am not satisfied that either of the 

 above names is correct ; nor have I been able to consult any conchologist in re- 

 gard to them, on whose opinion I can rely. . 



