GUPPY GULF OF PARIA. 
107 
them scoured out and the depth reaches 120 fathoms. This 
probably may be the extreme amount of the depression caused by 
the geological movements referred to in my papers. No mud or 
sand of any kind is deposited in these Bocas. The bottom is one 
of rocky inequalities whose existence is evidenced in the 
violent eddies and ripples of the so-called “ remu,” a phenome- 
non which occurs when the water outside the Bocas is at its 
lowest and consequently the water surface gradient from the 
middle parts of the Gulf the greatest. Outside the Gulf the 
Caribean Sea varies in depth from 20 to 60 fathoms except in 
the line of the great down-throw passing along the axis of the 
6* rand Boca. Here the depth attains 120 fathoms and is pro- 
bably not less than 90 in any part. This line of depression 
seems to be a terrestrial feature of some magnitude. Its exten- 
sion northeastward from the Boca Grande between the islands 
°f Grenada and Tobago is indicated by deep water marking the 
boundary between the volcanic region of the Antilles and the 
non-volcanic region to the south and east thereof. 
The rise and fall of the tide is from 2^ feet at neaps to 
about 4 feet at springs. We see in this the cause of the violent 
currents running through the Bocas. The vast body of water 
contained within the Gulf say 3,000 square miles to a depth of 
di feet to 4 feet is all impelled towards the Bocas by the fall of 
bde in the Caribean Sea. The outward currents thus caused 
are given in charts at 2 to 4 knots, but I think it probable that 
they sometimes exceed this very considerably. The statement is 
probably correct as an average, though the extreme force of the 
currents at particular times and in particular spots may possibly 
ev en attain a velocity of ten miles an hour. These currents 
exhibit a number of extraordinary “tide rips” which ^ry 
greatly at different tides. The phenomena of these tides are 
greatly modified by the state of the Venezuelan rivers, which 
Pour their waters into the Gulf, and which at times of heavy 
flood contribute so large an amount of water to the Gu 
bhus replacing what had passed out through the Bocas on the 
