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XIX., On the temperature at considerable depths of the Caribbean 
Sea. By Captain Edward Sabine, F.R.S., in a Letter 
addressed to Sir Humphry Davy, Bart. Pres. R. S. 
Read April 17, 1823. 
My Dear Sir, 
Wh e n I last quitted England, you did me the favour to di- 
rect my attention to the temperature at considerable depths 
of fresh water lakes within the tropics, or of basins of salt 
water out of the reach of currents from the polar regions, 
and in climates where the lowest temperature of the super- 
incumbent atmosphere is above 42 0 ., as the point of the 
greatest density of water ; viewing such knowledge in re- 
ference to the important question of the high temperature of 
the interior of the globe. 
It has bee 1 a subject of continual regret to me, that situ- 
ations in which the experiment could be tried, under circum- 
stances which would alone render it decisive of the point in 
question, are of such rare occurrence, that not a single oppor- 
tunity has presented itself to me on either side of the Atlantic, 
of carrying your suggestion into effect. As, however, it 
gave occasion to an attempt to ascertain the temperature of 
the Caribbean sea, at a depth beyond the means of sounding 
with which ships are usually provided, I may be permitted 
to take this mode o " acquainting you of the result. 
The Caribbean and Mexican seas, near the junction of 
which the experiment was made, approach the nearest, per- 
haps, to the character of insulated and deep basins of salt 
