358 J. D. Dana on the Consolidation of Coral Formations. 
cient reason for considering Prof. Horsford responsible for what 
he had thus published, and for subjecting his statements to a brief 
notice in this place. I was not present at the meeting of the 
Association where the paper was read. 
I propose therefore, to touch briefly upon some of the more ob- 
vious errors, misapprehensions, or inadvertencies, into which Prof. 
Horsford appears to have fallen. - 
I. Prof. Horsford’s investigations were made principally upon 
what he calls the “crust-rock,” one of the two kinds of coral for- 
mations which he mentions ; and this might be supposed from his 
descriptions to be a common form of the coral reef rock. In fact, 
it isan uncommon variety. I found nothing like it in my ex- 
plorations among the Pacific reefs and islands. The ordinary 
submerged reef rock, the prevailing rock wherever there are reef- 
regions, has no resemblance whatever to the “crust-rock,” and is 
distinct also from his “oolitic” rock. It is sufficient to account 
for the misapprehension which Prof. Horsford appears to be under 
respecting reef rocks, to state that he has never seen a coral reef. 
’ II. Some examples of a thin calcareous crust, are described by 
the writer as occurring in the Sandwich Islands. Prof. Horsford 
errs in regarding these as examples of his “crust-rock’’. The 
author has described them as a surface formation upon elevated 
hills of coral sand rock; that is, as mere surface crusts wpon the 
“ oolitic” variety of Prof. Horsford; it is of much more modern 
origin than the rock itself, and not one of the two prevailing va- 
rieties of reef rocks, any more than a stalagmite is an example of 
the rock which it encrusts. 
{ff. Prof. Horsford supposes erroneously that the explanation 
of the origin of this crust which I give, has been applied by me to 
the West India “crust-rock.” Not having seen that rock in place, 
I have offered nothing upon its origin or consolidation. 
IV. Prof. Horsford proceeds in his theory upon the supposition 
that the coral sands of seashores and submerged coral deposits of 
reef grounds, contain a large per-centage of animal matter. This 
conclusion, he has not sustained by an examination of these ma- 
terials from various regions: he is satisfied after an examination 
simply of some specimens of his “crust-rock ;” and proceeds at 
once to theorise for all coral formations: for if he does not say in 
so many words that his theory is intended for coral rocks generally, 
the manner in which he has replied to my objections, and the use 
us, to Dr, Gibbs, our collaborator in charge of chemistry and physics, and that if in 
his opinion its chemistry and statements of facts were correct, it would be published ; 
also, that if his former paper had been thus submitted, it would not have appeared 
in this Journal, on the ground of its incorrect chemical princi Siicn of 
reply been sent us, we should probably have saved Prof. Horsford the publication 0 
some of its errors. 
