Prof. Horsford on the Source of Lime in Corals. 253 
These facts seem to me to give some support to the view ex- 
pressed above. 
It was of interest to ascertain, in the case of corals, whether the 
formation of new coral without was attended with absorption or 
ascertained by Storer. ‘The average of three specimens from the 
centre, three from the middle, and two from the periphery, gave 
the following specific gravities :— 
Centre. Middle. Periphery. 
2,695 2,749 2,785 
These results so far support the affirmative of the suggestion above, 
as to make a repetition of the determinations desirable. 
The chief conclusions to which the above research has con- 
ducted are :— 
I. That the submerged or oolitic rock has been solidified by 
the infiltration of finely powdered (not dissolved) carbonate of 
lime, increasing the points of contact; and the introduction of a 
small quantity of animal mucilaginous matter, serving the same 
urpose as the carbonate of lime, that of increasing the cohesive 
attraction. 
_ IL. That the surface rock has been solidified by having, in ad- 
dition to the above agencies, the aid of a series of chemical de- 
Compositions and recompositions resulting in the formation of a 
cement 
And I may add that it lends support to the suggestion, 
IIL. That the carbonate of lime of corals is derived from the 
sulphate in sea-water, by double decomposition with the carbonate 
of ammonia exhaled from the living animal. 
_ [Note.—Mr. Dana will add some farther explanations and — 
cisms on the subject of Prof. Horsford’s paper in another ameener 
of this Journal.—Ebs. | 
