J. D. Dana on some modern Calcareous Rock-formations. 413 
_ Prof. Horsford assumes that consolidation is due to the agency 
of the sulphur present in the animal matter mixed with the coral 
sand or mud. ‘The analyses he publishes make out that there 
we have not definite analyses. We only ajserve that the mud 
when dried is generally white like chalk or sand and nearly to all 
appearance as pure; it could not be one-fifth animal matter with- 
out showing it in an offensive odor, as observed by Prof. Horsford 
with reference to the Florida material. ae 
Instead of the “dying animals falling upon and mingling with 
the coral mud of the bottom,” a considerable part undergo com- 
plete decomposition ; another part are washed away by the sea; 
One-fifth part by weight is a large eee Ee ei een 
i l. ivi , Astrea or Porites is a 
De tiie neces 124 il depth, the rest being 
* Me. Darwin, speaking of a large beach of calcareous sand com ed of com- 
i led fr: rals at Ascension, says, “The 
munuted and fragments of shells and cot as me Boer ett an 
round 
por iyi emda Arp sie a building stone ; but some of the 
layers are too hard for fracture, and when struck by the hammer, ring like flint. 
Journal, p. 587, z 
Sreoxn Sznres, Vol, XIV, No. 42.—Nov,, 1852, 63 
