J.D. Dana on some modern Calcareous Rock-formations. A11 
% tobe a duty to science to pass the principal points of his paper 
view. 
Prof. Horsford, after describing the coral rocks of the Florida 
reefs as of two kinds, a subaerial and submarine, the former 
stated to be a kind of crust deposit, the latter oolitic, alludes to a 
calcareous crust, mentioned by the writer as occurring in the Pa- 
cific, as a case of the former kind. We remark, in the first place, 
that this distinction, imputed to the West Indies, does not exist 
in the Pacific, as will be gathered from the author’s descrip- 
curring especially in depressions. Whatever may be true there- 
fore of the rock in the West Indies, it is erroneous to speak o 
the crust, which the author has described, as an example of the 
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harder and more compact than the subaerial rock ; and although 
sometimes conglomerate in character, it 1s frequently as solid and 
as free from grains as any Silurian limestone of the United States. 
« : 
Among the modes of consolidation of lifnestone or carbonate 
of lime, the following are enumerated by Prof. Horsford :—1. the 
co; 
 blufis.so fluted by the waters trickling down their front, and 
80 streaked with stalagmitic incrustations, that at a short eon 
at sea they appeared to be made up of basaltic columns: an Z 
open excavations or caverns in its cliffs abound in stalactites o 
“ huge size, some enclosing recent Helices that have been covered 
over and entombed while hybernating. Through the elevated 
