G. HUGHES ON WEST-IXDIAN PHOSPHATES. 81 



the phosphatic guano upon the surface ; but the solid rock is now 

 rich phosphate. From these specimens of the phosphatized coral 

 it will be seen how complete has been the change, and at the same 

 time how perfectly the coral has retained its structure. 



These specimens of phosphatized coral yield from 78 to 80 per cent, 

 of phosphate of lime, and, so far as the deposit has been shipped as 

 yet, the cargoes have tested over 76 per cent, of phosphate. 



Analysis of a Sample of Aruha Phosjohate. 



Moisture "62 



Water of combination and traces 



of organic matter 2"91 



Phosphoric acid 35'70 (equal to tribasic phosphate 



Lime 46-37 ofHme 77-93) 



Oxide of iron 1-80 



Alumina 2"95 



Carbonic acid 1-53 (equal to carbonate of lime, . . 3-54) 



Sulphuric acid 1*55 



Fluorine &c 4-22 



Silica 2-35 



100-00 



Other deposits of phosphates found in the "West Indies owe their 

 origin to direct marine deposit of bone, as, for instance, that of 

 Curacao. In the next island to Curacao (Bonaire) I have seen the 

 coral over an area of two miles to contain fossil bones and teeth 

 scattered in all directions. The specimens I have the pleasure of 

 showing you from that island give a very good idea of how these 

 bones occur ; and had they been deposited in one spot, as in 

 Cura9ao, we should have been able to have worked a good deposit. 



Discussion. 



Mr. B. B. WooDWAEi) asked if in the West Indies the same con- 

 ditions were found as in some of the islands of the South Pacific, 

 namely, the carrying-down of phosphates into the mass of the coral- 

 reef, and the subsequent removal of the carbonate of lime leading to 

 the formation of casts of corals in the phosphate of lime. 



Prof. T. Rupert Jones asked if there are any guano-islands in the 

 West Indies now. 



Mr. Htidleston asked if the facts observed threw any light on the 

 formation of the phosphatic layers in the Cretaceous rocks. 



The Author replied to Mr. Woodward that he had not observed 

 casts of corals in phosphates found in the West Indies. To Prof. 

 T. Eupert Jones, that guano-deposits are still in course of forma- 

 tion, as, for example, in the Monks Islands near Aruba. The rain, 

 however, dissolves out the soluble phosphates, which are lost, as the 

 rocks on which these deposits occur are of a siliceous nature. The 

 insoluble portion of the guano forms a crust upon the rock. To 

 Mr. Hudleston, that this replacement of carbonic acid by phosphoric 

 acid might throw light upon the formation of phosphatic layers in 

 the Cretaceous rocks. 



Q.J.GS, No. 161. Q 



