1878.] AT [Crosby. 
shallower; and, moreover, the encroachment of the sea on this coast 
must for a long time proceed very slowly on account of the range of 
hills — three hundred to seven hundred feet high, which the waves 
have just begun to act upon. When the geographic changes here 
indicated are complete, the main mouth of the Orinoco will have 
made an appreciable advance eastward; Trinidad will be included 
in its delta; and the Dragon’s Mouth will form another principal 
mouth of this mighty river, discharging water direttly into the 
Caribbean Sea. 
The origin of the Dragon’s Mouth itself is justly regarded as one 
of the most interesting problems in the physical geography of Trin. 
idad; and various are the solutions which have been proposed. 
Subsidence, however, is a feature common to them all. According 
to the most recent view, that advanced by Mr. Guppy,? this subsi- 
dence is local, and results from a grand fault running in a N.—S- 
direction along the west side of the Dragon’s Mouth, having the 
downthrow on the east, and producing at once the strait in question 
and the Gulf of Paria. Iwill preface my view with a statement of 
the principal facts. 
The Dragon’s Mouth (or Boca ?), from the Point of Paria to the 
main land of Trinidad, is thirteen miles wide. The three islands — 
Monos, Huevos, and Chacachacare — lying in the eastern half of the 
Dragon’s Mouth, divide it into four distinct channels or bocas. The 
first three bocas, reckoning from the east, average about one mile in 
breadth, while the fourth boca, Boca Grande, is over seven miles 
wide at the narrowest place. Pato Island lies too far to the south of 
the Boca Grande to be said to divide it. The bocas are deep, and 
the separating islands high and mountain-like. The maximum 
depths, beginning with Monos Boca, are 35, 60, 75, and 145 fath- 
oms, respectively. 
That subsidence has been the main cause of the bocas is rendered 
certain by an examination of the boca islands, and the cross sections, 
as determined by soundings, of the bocas themselves. The areas. 
of these islands range from one and a half to three square miles, 
and the maximum altitudes from seven hundred to one thousand feet. 
They have precisely the forms and contours of the higher peaks of 
the adjacent mountains of Trinidad; and are, in fact, simply par- 
tially submerged mountains. They are deeply indented by bays; 
these, as a rule, however, have very plainly not been excavated by 
1 Proc. Sci, Assoc. Trinidad, 1877, p. 104. 
2 Spanish for mouth. 
