G2 Professor Horsford on the 



To these chemical changes must be added the simple ad- 

 mixture of the animal and vegetable matter, which, like 



" In the first place, his (Prof. H.'s) paper only alludes to the rock formed 

 ahovc low-tide level, which I have called the coral sand-rock. Again, the 

 amount of organic matter in corals, as found by analysis, does not exceed five 

 per cent. ; and the sulphur present in this organic matter, is not over one-tenth 

 of one per cent. It hence appears that the amount of sulphur is altogether im 

 adequate for such changes. 



" But as the sands of the beach (which have a peculiarly white and clear ap- 

 pearance) are washed by the breakers, and the animal matter they contain is 

 either undecomposed within the several grains, or is borne off by the waters, 

 even the animal matter present cannot contribute to the consolidation. The 

 waters of the tides along a sand beach on the open ocean have certainly not 

 been proved to carry in dissolved animal matter for dissemination among the 

 sands." 



Two or three points in this note demand attention from me. 



The first sentence of the first paragraph should be read in connection with 

 the conclusions I. and II., expressed at the end of my paper. 



In reply to the remainder of the paragraph, the criticism would be just, if I 

 had any where ascribed the solidification, or any part of it, to any action of 

 the organic matter in corals. 



Since the publication of my article in the Proceedings of the Association, 

 there have been made quantitative analyses of the more important ingredients 

 of the soft rock, corresponding, as I conceive, with the rock of sub-aerial soli- 

 dification in the first stages of its formation. When first supplied to me, it 

 was of the consistency of well-tempered pottery clay. It is now so hard as to 

 yield only to a severe blow with a hammer, and is, beside, brittle and coated 

 with fibrous crystals of common salt. 



The following analyses made by Everett and Warren, upon samples differing 

 but little from each other in appearance, have been conducted with great care. 

 They vary, it will be seen, considerably from each other : — 



Dried at a temperature of 100° C. By prolonged ignition. 



I. 1-1450 gr. lost 0-0890 gr. 0-8270 gr. lost 0-4870 gr. 



II. 1-5325 gr. lost 0-1175 gr. 1-9020 gr. lost 0-8000 gr. 

 The hydrochloric acid solution left a residue of organic matter. 



I. 1-1450 gr. gave 0-2930 gr. II. 1-6424 gr. gave 0-2805 gr. 



The mass, digested in diluted hydrochloric acid, yielded from existing sul- 

 phate upon the addition of chloride of barium to the filtrate, sulphate of baryta. 

 I. 2-3380 gr. gave 0-1040 gr. II. 1-5325 gr. gave 0-1304 gr. 



The organic matter by itself, oxydated in nitro-hydrochloric acid, with addi- 

 tion of pulverized chlorate of potassa, yielded to chloride of barium a precipi- 

 tate of sulphate of baryta. 



I. 1-5325 gr. gave 0-1505 gr. 

 The whole mass oxidated in a mixture of fused nitrate of potassa and car- 

 bonate of soda, yielded to chloride of barium and hydrochloric acid, a precipi- 

 tate of sulphate of baryta. 



