J. J. Dana on the Consolidation of Coral Formations. 363 
XII. To the principle, abundantly exemplified, that on shores 
where the waves break heavily, beds of pebbles or sand are pro- 
profound problem, which may be paralleled, and perhaps eluci- 
dated in some slight degree, by the enunciation of another of 
equal significance, bearing upon the laws of motion in general :— 
If the slower a coach moves the longer it will take to go a mile, 
how long will it take if it does not go at all: 
XIIL. Prof, Horsford passing from reef-rocks to coral polyps, 
suggested with reference to the secretion of carbonate of lime 
that “the carbonate of lime of the coral, was the fruit of simple 
double decomposition of the sulphate of lime in sea water, by the 
carbonate of ammonia exhaled from the living coral.” To this sug- 
gestion I objected in my former paper, on the ground that the ex- 
eretions could not turn about and aid in the secretions.* He now 
says, “it appears to me that the precipitate of carbonate of lime 
under the circumstances supposed, would take place in the walls 
of the cellules, where the carbonate of ammonia is set free, and 
would of course take the form of the cellules:’’—thus making the 
secreting cellules produce, contrary to all that is known, carbonate 
of ammonia, one of the results of the ultimate decomposition of 
animal matter. 
XIV. The deposition of carbonate of lime from calcareous 
waters is the last point which I will now mention. Prof. Hors- 
ord commences his observations on this subject as follows : 
“ He (Prof. Dana) remarks: ‘Among the modes of consolidation 
the manuscript, E. N. H.) give up the carbonic acid so that a precipi- 
tation of the carbonate of lime takes place. But is this pressure or a 
* I have stated in my report, that the coral polyps have probably the power of 
deriving the lime by secretion from the sulphate of lime present in the waters ; 
but I have not undertaken to point out the exact character of the change, as 
question has not been investigated. 
