60 SOUTH AMERICA— THE ANDES REGIONS. 



certainly be found in this district. As it is, tlie detritus must be regarded as the 

 débris of cliffs undermined by the marine waves beating against the foot of the 

 hills raised by successive thrusts above sea-level.* 



The central districts comprised between the northern and southern coast 

 rano-es present in the neighbourhood of the sea extensive expanses which were 

 formerly marine inlets ; now they are filled to a great depth with alluvial matter 

 formed by the decomposition of mangroves and other plants. Possibly to the 

 presence of this fluvial sediment is to be attributed the absence of continuous 

 coralline formations on the coasts of Trinidad. Here and there, however, there 

 occur a few coral reefs, fragments of which are strewn on the beach after every 

 storm. The gradual subsidence of this part of the coast is placed beyond doubt 

 by the numerous dead tree-stems on the beach, killed by the surging tide.f 



Eeference is often made to " volcanoes " in various parts of the island ; but 

 there exist only some groups of " mud volcanoes," one of which, towards the 

 centre of the island, rises 135 feet above a morass called the " Lagon Bouffe " by 

 the Creole negroes. Those of Cape Icacos at the south-west extremity, surrounded 

 by swamps and fringes of mangroves, are conic hillocks, some mere molehills, 

 others from 14 to 16 feet high. All are pierced by a terminal vent, whence 

 escape periodical ejections of a whitish substance tasting like alum, and emitting 

 an odour like that of sulphuretted hydrogen. The muddy waters bubbling up to 

 the surface have no higher temperature than that of the surrounding atmosphere, 

 although they at times eject shingle and lumps of sulphur with great force. 

 According to the residents the Cape Icacos mud volcanoes utter bellowings every 

 year about the spring equinox, and at this period also are said to occur the erup- 

 tions of pebbles, accompanied by the uprooting of trees. 



An old map indicates in the Gulf of Paria an islet which was said to have made 

 its appearance simultaneously with a violent earthquake on the neighbouring 

 mainland. In several parts of the south-western peninsula are seen beds of 

 porcellanite, clays, and vitrified sands which have assumed the appearance of 

 jasper. These beds, which are of no great thickness, and which occur in the 

 midst of the quicksands, have evidently been exposed to the action of fire, like 

 the slag of smelting furnaces, and they are supposed to have resulted from the 

 burning of asphalts or lignites. 



This part of the coast also appears to be in process of subsidence like that 

 of the east side. Thus two forces acting in opposite directions are continually 

 modifying the contour-lines of the island — that of the currents depositing sedi- 

 ment on the beach, and gravity or some other agent causing certain parts of the 

 coast to sink. 



The Asphalt Lake, 



In the same south-western peninsular district is also situated the " marvel " 

 of the island, the so-called Brea, or As^jhalt Lake, one of the greatest natural 



* G. P. Wall and J. G. Sawkins, Report on the Geologij of Tiinidad. 

 t Charles Kingsley, At Last, a Christmas in the West Indies. 



