210 Captain Edward Sabine on the temperature, &c. 
of Monsieur Perron, the imperfection of whose apparatus 
prevented his obtaining equally decisive results. Being un- 
provided with a registering thermometer, he enclosed one of 
the ordinary construction in several cases filled with non- 
conducting substances, in order that the temperature which 
the thermometer had acquired, by being suffered to remain 
a sufficient time below, might not be disturbed by its being 
drawn up through the warmer strata. It appears, however, 
that in his principal experiment, in which the apparatus was 
sunk to 2144 feet, the process of raising it lasted three-quarters 
of an hour, or half the time it had remained below : the diffe- 
rence therefore between the surface and the deep sea water, 
may be supposed to have been actually greater than would 
appear in his results ; they are in accord however with the 
present, in showing even a more rapid decrease of tempe- 
rature in descending from the surface. 
In lat. 5 0 North, s8° degrees of Fahrenheit less than at the 
surface at 1200 feet; and in lat. 4 0 North, 42 degrees of 
Fahrenheit less than at the surface at 2144 feet. 
The thermometers used in the present Experiment were 
made expressly for the purpose to which they were applied, 
and were of the ordinary construction of Six’s registering 
thermometer : the top of the tube, in which is contained the 
index of heat, was hermetically sealed instead of being closed 
by a cork, as is sometimes the case. I have no reason to doubt 
the accuracy of their performance in any respect. 
I remain, my dear Sir 
your obliged and faithful Servant, 
2, Portland Place, EDWARD SABINE. 
March 18, 1823. 
