287 
Guppy Reprint 
139 
in a shallower sea than the true oceanic beds and one wherein the 
conditions varied somewhat from those. 
During the cretaceous period the Amazonian and Orinocan 
region was occupied b}' sea as shown b}^ Karsten ( Geogno,stiche 
Verhaltnisse des westlichen Columbien), while at the same time 
a portion of the Atlantic Ocean was occupied by land. As ex- 
plained in my papers (“Growth of Trinidad’’ and “Geological 
Connexions of the Caribean Region,’’) the .sediments of which 
the rocks of Trinidad are composed were up to the end of the cre- 
taceous period derived from the land which existed to the north 
and north-east. But upon the clo.se of the cretaceous period and 
the gradual rise and filling up of the Amazonian and Orinocan 
region, the sediments now came from the west and .south-west 
inaugurating the period of asphaltic and carbonaceous deposits 
which probably continued throughout the tertiary period. 
The origin of the carbonaceous .substances is to be found in 
the va.st quantities of vegetable matter brought down by the 
rivers from the continent of South America. This matter being 
of a slighth" greater specific gravity than water, is subject to the 
laws wdiich govern the removal and deposition of sediment or 
clastic material. Now one of these laws is that material of like 
specific gravity and of like finene.s.s or coarseness of grain or di- 
mensions of the component parts is deposited together and apart 
from dissimilar materials. Hence the vegetable matter brought 
down by the rivers was deposited in layers banks or strata be- 
coming interstratified with other sedimentary materials as the 
process of sedimentation and depo.sition went on. Chemical 
changes supervened which converted the vegetable tissues into 
the forms in which we now find them, nameh' Lignite, 'Asphalt, 
Manjak and Petroleum. 
P. S. — Basing my opinion on the theory expounded above, 
I predicted two or three j’ears ago that petroleum would be found 
in the deltas or sedimentary formations at the mouths of tropical 
rivers. The prediction has already been verified in the cases of 
Nigeria and Tampico. 
