HILL: GEOLOGY OF JAMAICA. 195 
accumulation represent portions of the windward sea bottom which 
was brought up by uplifts of the main chain. 
This main or interior chain is composed of piled up volcanic debris, 
and upon the islands of Guadeloupe and St. Vincent there have been 
active volcanic eruptions in historic time, 1797 in the former and 1812 
in the latter. Soufriéres, hot springs, etc., show that this activity is 
only slumberingly quiescent in nearly all these islands.  Desides most 
of them still possess upon their summits one or more true craters, 
while Saba and St. Eustatius are composed of simple crater cones now 
quiescent, While these facts attest recent eruptivity in the islands, 
there is much evidence presaging the conclusion that the present 
vuleanism is merely the survival of that which began much earlier in 
geologic history. 
The configuration and structure show that their history extends back 
to considerable antiquity. In the first place while the protuberance 
of all these islands is largely due to extrusive piling up, the present 
detailed configuration expressed in steep coastal bluffs, benches, slopes, 
and canyons, is produced by erosion, which has required considerable 
time for development. True crater shapes, except in St. Eustatius and 
St. Christopher, are exceptional and are merely Secondary summit 
features in the other islands, occurring parasitically upon masses of old 
eroded volcanic débris reaching a height of 4,000 feet. Secondly, they 
are all composed largely of vast piles of old tuffs and trachytic débris 
of many eruptive epochs, like the volcanic heights of the Costa Rican 
plateau, which indicate long continuation of the volcanism since com- 
paratively remote geologic epochs, reaching back most probably to the 
Eoceno time. 
In St, Christopher, St. Eustatius, Guadeloupe, Martinique, St. Lucia, 
and Granada, disturbed fossiliferous beds of Pleistocene or recent age 
are found interbedded in volcanic débris of the lower slopes at altitudes 
Of two or three hundred feet above the sea, showing that uplifting as 
Well as extrusion has in part produced the present eminences, and that 
Vulcanism existed in Pleistocene time. 
The fossils mentioned are hardly older than Pliocene, and are most 
Probably Pleistocene, and their border-like position shows that the 
greater mass of the islands were ejected in previous epochs. 
So much for the main chain of the Caribbees considered by them- 
Selves, but the eastern belt, of the compound type, owe their present 
Position above sea level to the orogenic uplifts which affected the 
Caribbean area in later geologio time. Guadeloupe and Antigua are the 
