252 Prof. Horsford on the Source of Lime in Corals, 
depth of four hundred and twenty feet, in various latitudes on 
both sides of the equator, shows quite conclusively that it is not 
a constant ingredient of sea-water. Hisanalyses do not mention 
a trace of carbonate of lime. The quantity found by Davy is 
very nearly that which is soluble in water, and is obviously due 
to the calcareous marl which abounds near the Barbadoes. 
The water from within the Keys was carefully analysed in my 
laboratory: it contained lime and sulphuric acid among its ingre- 
dients, but not a trace of carbonic acid. 
The total want of carbonic acid in a water in which coral life 
is so luxuriant, suggests naturally that the stone plant, as well as 
the coral animal, possesses the power of abstracting lime from 
the sulphate; the change being due to double decomposition 
with carbonate of ammonia excreted from the plant and animal, 
yielding carbonate of lime, quite insoluble, and sulphate of am- 
monia of the highest solubility, The building up of the calcare- 
ous skeleton becomes, upon this hypothesis, of exceeding sim- 
plicity. The surrounding element yields at once to the exhaling 
carbonate of ammonia the framework of stone. 7 
With this view, there is no difficulty in finding a supply of car- 
bonate of lime for the vast masses of coral. The sulphate of lime, 
decomposed to furnish the carbonate, is perpetually renewed 
through rivers from the continents and islands. . 
_ The following inferences are legitimately deducible from this 
iew :— 
Ist. Corals would soon die in bodies of salt water wholly cut 
off from the ocean. ite! 
2d. They might flourish to some extent in waters accessible 
to the sea only at high tide. 
In Dana’s Report on Coral Reefs and Islands,* he states that 
“where there is an open channel, or the tides gain access over 
a barrier reef, corals continue to grow, ete. At Henuake the sea 
is shut out except at high water, and there were consequently 
but few species of corals, ete. At Ahii there was a small entrance 
to the lagoon; and thongh comparatively shallow, corals were 
growing over a large portion. 
* Am, Jour. Science, [2] xii, 34 to 41, and Geol. Report Expl. Exp, P 63. 
+ In my article, as published in the Proceedings of the Association, I have 
Dana’ i i 
uoted from Prof. s papers in support of other inferences deduce ad from ia 
oregoing vie have since lea m the author that I had misconceived ad 
nse in which the q tions were be rstood, and hay me 7 f. 
especially after examination of the map of the H yr 
Dana’s last article, he inference that fresh water streams, by their suP| ply 
sulphate of lime, exerted any considerable influence upon coral fi Jons, 18 
e of li -water, however, being one-sixteen' the 
