266 R. T. HILL — PELE AND THE WINDWARD ARCHIPELAGO 



Antigua, Saint Croix, and the Anguillan group of banks of the northern 

 section in their structure, composition, and origin present a foundation 

 of volcanic tuffs and agglomerates similar in composition and nature to 

 rocks of the present volcanic Caribbees. It is not unreasonable to infer 

 that Barbuda, Anguilla, Dog, and other small calcareous islets composed 

 entirely at their surface of oceanic material likewise rest on volcanic 

 basements. 



No sources other than the earth's interior and pure oceanic water have 

 contributed matter to the land masses of the Windward islands. In the 

 clear sea waters surrounding the Windward islands invertebrate organ- 

 isms abound, which are constantly concentrating from the sea water the 

 carbonate of lime which constitutes their skeletons. Foraminifera, mol- 

 luscs, and corals live and die on the shores and slopes, contributing their 

 load of solid material to the land masses. The quantity of organic ma- 

 terial, although but small in comparison to the volcanic ash already 

 exposed in the sections of the islands, is large, while in the submerged 

 slopes of the ridges a still greater quantity, though unexposed, un- 

 doubtedly occurs. 



This process of rock-making by organisms, although not given suffi- 

 cient consideration in text-books, is well known to all students of coral 

 reefs and tropical oceanography. Its operation in the West Indies has 

 been fully described in the writer's report on Jamaica. 



The geologic structure of the Windward islands is likewise exceedingly 

 simple and owes its arrangement chiefly to volcanic processes. It con- 

 sists primarily of constructional volcanic piles, with material arranged 

 at various degrees of inclination, in accord with the well known laws 

 of the angle of rest and submarine beds of sedimentary material. Def- 

 ormation of any kind except local land slips is inappreciable. The only 

 modifying structural processes are those of unconformities produced by 

 littoral marine erosion, the deposition of organically extracted lime 

 accretions on the planed-off volcanic foundations, and the oscillations 

 of regional uplift which are supposedly connected with vulcanism. 

 There should be some instances of local folding or faulting, but trust- 

 worthy evidences of these phenomena are lacking. 



It is true that in the east-west Antillean trend to the northward there 

 are great fault lines, and the same may probably be true along the east- 

 west South American trend. In Barbados, to the east, we find serious 

 pre-Pliocene deformation, but in the main north-south Caribbee ridge 

 no trace of marked displacement or Assuring by deformation has been 

 discovered. 



If Assuring exists of a size sufficient to feed the roots of the Caribbee 

 volcanoes with water, as alleged by some recent writers, or if these have 



