700 THE GEOLOGY OF ANTIGPA. [NOV. 10,11, 



went on. Chemical changes supervened which converted the vegetable tissues 

 into the forms in which we now find them — namely, lignite, asphalt, manjak, 

 and petroleum.' l 



EXPLANATION OF PLATE L. 



Map showing the trend of the great Antillean dislocation, on the approximate 

 scale of 28 miles to the inch or 1 : 1,775,000. 



Discussion. 



Mr. G. P. Wall, after referring to bis long-standing acquaintance- 

 ship with the Author, which extended over more than half a century, 

 remarked that the geological conditions in the West Indian islands 

 were highly complicated, and it was difficult to collate or synchronize 

 the formations with those of the well-known European series, or 

 those of other areas. Moreover, it might be that the climate and the 

 environment of the tropics had not varied so much during Tertiary 

 times, and had not, therefore, involved that change or modification 

 in the succession of organisms which was so marked in temperate 

 climes. 



In Eastern Venezuela there was a great development of Lower 

 Cretaceous strata, comprising vast beds of indurated limestone 

 rising to altitudes of 7000 feet ; the same formation was found in 

 New Granada and the range of the Andes, a fragment being 

 prolonged into Trinidad. This mountainous district was known 

 as the Serrania, while the Llanos consisted of undulating grassy 

 plains dating from Tertiary time. Similar developments of Lower 

 Cretaceous existed in the Jura district, where lofty, highly inclined 

 escarpments of compact limestone rose to great elevations, as at 

 Sonceboz (11 miles from Bienne) and in the Minister Yalley. 



In Jamaica the Cretaceous was of later age, belonging to the 

 Hippurite stage. The eastern portion of that island was moun- 

 tainous, rising to 7500 feet, and the fossils were found in a crystalline 

 state ; but in the western districts the conditions were simpler : the 

 Clarendon Yalley had a floor of slightly arched limestone, crowded 

 with Caprina and allied genera. Rising on the flanks of this 

 valley were marls and loose sands full of foraminifera, probably of 

 transition or Eocene date — succeeded by the locally termed ' White 

 Limestone ' — a dense rock of great thickness and extension (also 

 developed in the adjacent large island, Santo Domingo) and recog- 

 nized as belonging to the Miocene Period: finally came the more 

 recent coastal and other beds of coralline and loosely aggregated 

 strata. It would appear, then, that the floor of the Caribbean Sea 

 consisted in part of Lower, in part of Upper Cretaceous rocks, 

 through which igneous eruptions had burst, forming the entire 

 structure of several of the islands — and well shown on the Soufriere 

 of St. Vincent (3000 feet), where alternations of beds of lava, ashes, 

 and scoriae were inclined in proportion to the elevation, just as in 

 other volcanic masses (as, for example, Etna) which have been built 

 tip by eruptive outbursts. 



1 See Crosby, ' Native Bitumens & the Pitch Lake of Trinidad ' American 

 Naturalist, April 1879. 



