80 Geology of Antigua. 
hood of Si. 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 eran on one of which stands the 
cathedral. 
At this place, tH chert i is strangely intetmirigled 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 anne the other, 
or where they came directly in contact. 
The aspect of this rock is various ; generally, fowaren highly 
vitreous. It sometimes approaches to jaspet, 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 werbstiniis 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 
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 Melanie.* These shells 
are ibways 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 
4 De Nugent calls these shells cerithium. I am not satisfied that either of the 
‘Thames is correct; nor have I been able to consult any conchologist i in re- 
opinion | can rely. _ 
gerd to'thaen, noes 
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