T2 Geology of St. Croiai. 



few more delicate shells of the genera Serpnla, Liicina, Voluta^ 

 Bulla, &c. ; all these species still inhabit the surrounding seas. 

 In addition to this fact, there are other circumstances which show 

 the recent origin of this deposit. This part of the coast is liable 

 to a strong surf, which is constantly drifting shells and other sub- 

 stances upon the shore, and dashing over them spray charged 

 with calcareous matter. These generally unite and harden, espe- 

 cially near the surface, and form into a tolerably compact mass. 

 I also found imbedded in these rocks, iron utensils, which had 

 been employed at no very remote period, in quariying them. It 

 contains many fragments and rounded pebbles of indurated clay, 

 which as a generah thing unfit it for the kiln. 



Though it is obvious these rocks are still in the process of for- 

 mation, they have been much abraded and broken by the surf. 

 I doubted, indeed, for some time, whether they could have been 

 formed in the face of such powerfully abrading agents ; but the 

 fact, that the windward coasts of coral islands are generally dis- 

 tinguished by the greatest accumulations of matter, removes the 

 diificulty. I saw in one place a mass of rock containing about four 

 hundred cubic feet, which had been detached from its bed, raised 

 several feet, and thrown back upon the shore. This deposit every 

 where rests upon the tilted strata of the indurated clay, which 

 often form a precipitous bank, and generally rise within a short 

 distance into high mountains. The shore is lined with tropical 

 shrubs and trees, such as Hippomane mancinella, Guilandina 

 bonducella, Coccoloba uvifera, Lantana involucrata, Turnara ul- 

 mifolia, Mimosa spinosa, (fcc. 



The marl varies in composition, and hardens even within mod- 

 rate distances. It often comprises extensive beds of lime nearly 

 pure, and so soft that it may be dug with a hoe ; in other places, 

 it is mingled with sand, becomes harder, and forms a good build- 

 ing stone. In such cases, it is easily broken at first, but hardens 

 by exposure to the atmosphere. ' In structure and general aspect 

 I saw quarries much resembling those of the Paris basin, from 

 which such ample materials for building are derived. 



It is impossible to draw a dividing line between these beds and 

 the purer lime deposits on the south and west. Both are no 

 doubt contemporaneous, and owe their difference to peculiar cir- 

 cumstances in their deposition. The limestone sometimes occurs 

 in a compact form ; but the structure is generally loose and fria- 



