120 ROYAL SOCIETY OF CANADA 
It is also possible that in the broad area between the crystalline 
rocks and the anticline which extends from San Fernando to Manzanilla 
areas of Tertiary oil-bearing rocks may occur. The geology of this dis- 
trict has not yet been carefully mapped, but deposits of lignite coal 
oceur in the eastern area to the south and east of Sangre Grande. 
The course of these anticlines is indicated at several places by the 
presence of mud volcanoes and oil-springs, escaping gas and outflows of 
asphalt, as well as by the opposing dips to the north and south. Thus 
the celebrated Pitch Lake is very closely associated with the line of anti- 
clinal which extends across the island to Mayaro point, and similar 
occurrences of asphalt, though on a much smaller scale, are found along 
its supposed course at intervals, although a large part of the country 
supposed to be traversed, especially in the eastern ‘portion, is nearly 
inaccessible owing to its jungly and often swampy character. Similar 
occurrences of asphalt have already been alluded to as occurring in con- 
nection with the Guaypo anticline, as also with the most southerly one 
near the eastern extremity, where the principal borings have been made, 
and where the outflow of the hardened oil covers an area of several acres. 
According to the work of the Government geologist certain portions of 
this anticline belong to the underlying Cretaceous, which has been 
brought to the surface either by faults or by denudation of the Tertiary 
rocks, 
In descriptions of Trinidad reference is always made to the Pitch 
Lake. For many years its origin has proved an interesting source of 
speculation on the part of certain scientists, and a number of theories 
have been advanced to account for its presence. Some of the published 
descriptions are not strictly in accordance with the observations recently 
made. 
As seen at the present day it presents a fairly uniform level surface 
of black or brownish-black asphalt or pitch, with an area of about 127 
acres, the careful recent measurements having shewn that the actual 
outlines are somewhat larger than was formerly supposed. 
The surrounding shores are formed for the most part of sands, are 
of somewhat irregular outline and fringed with trees and other tropical 
vegetation. The surface is somewhat deeply fissured in various direc- 
tions the fissures being filled with water. In ordinary dry seasons the 
surface of the asphalt is quite free from water except such as is con- 
tained in these fissures, but in the rainy season the whole surface 
becomes covered, the surplus water being drained off by a large ditch, 
which is cut through the north-west angle, and is discharged into the 
sea, a distance of nearly one mile. 
