I have observed the same effect myself taking place in the West 

 Indies, where the surface of the coral rock is speedily converted into 

 phosphate of lime, wherever the seabirds are in the habit of 

 congregating. 



Such indeed is the simple origin of some of the most important 

 deposits of phosphate in that portion of the world : i. e., Curacao, 

 Sombrero and Aruba, etc. 



The prospecting and first development of the latter named 

 island having fallen to my own care and experience, I am able to 

 produce some interesting specimens here, illustrating very clearly the 

 history ot their formation, by examination of their fossil organisms, 

 originally carbonate of lime (coral rock), and now seen to be, by 

 analysis, phosphate of lime of over 80%. 



The deposits of Florida and South Carolina would appear to owe 

 much of their phosphatic wealth to debris of phosphatized limestones 

 and marls. 



One of nature's operations, which is a factor in enriching already- 

 formed phosphate beds, may be here alluded to, namely, the property 

 of spring waters (which often contain considerable proportions of 

 bicarbonates and free carbonic acid) to disolve neutral carbonate of 

 lime, even when presented to them in apparently as the most compact 

 and impervious material. Such has been the origin of the many 

 remarkable caves existing in the limestone rock formations (Cheddar, 

 Derby, Kentucky, etc.) 



I'his property applied to a calcareous phosphated mUerial will, 

 in course of time, ablate, as it were, more carbonate than phosphate, 

 and to this action is attributed the value of many thousand tons of 

 material, in such extensive beds as those of the Somnie, Ciply, Liege, 

 and probably of Florida. 



While speaking of these beds of the Cretaceous period, I may 

 mention the recent opening up of another similar field in France. I 

 refer to that in the department of the Pas de Calais, which would 

 appear to be of the same nature as that of the Somme. 



APATITES. 



Although crystallized phosphate of lime is found as a component 

 ot rock masses in more recent strata, yet we do not yet know of any 



