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depths were not so great as seriously to interfere with their 
performance. And you will observe that whether those thermo- 
meters had been in error or not (which we did not know till 
we tried), the same effect would be produced in raising the 
mercury at 500 fathoms, whether it was in the warm or the 
cold area ; so that the difference of the warm and the cold — 
between about 32 and 47 degrees — would be just the same. These 
thermometers having been a couple or three degrees too high — 
as they proved to be — we found that the temperature of the 
first year, which had been 32°, became 30°, and that which 
had been 47° was really 45°. But the difference of 15 degrees 
was exactly the same ; and the conclusions at which we had 
originally arrived in regard to it were verified in the very 
careful, numerous, and elaborate inquiries which we prosecuted 
over this area the next year. The most remarkable contrasts 
of bottom - temperature were shown at different depths on the 
southern slope of the channel. Thus, at a depth of 190 fathoms 
the temperature was 48°*6 ; whilst only eight miles to the 
north, where the depth had increased to 445 fathoms, the ther- 
mometer sank to 30 o, l ; thus showing a difference of bottom- 
temperature to the amount of 18 ° within that short distance, 
with a difference of only 255 fathoms in depth. 
Again, we took what I have called “ serial soundings ; ” that 
is, we let down our thermometers at different depths, for instance 
at 50 fathoms, then at 100, then at 150, then 200, then 250, 
and so on every 50 fathoms ; and the results we got are shown 
in the diagram, which is so constructed that a curve indicates 
the descent of the thermometer, and the depths are expressed 
by the horizontal figures, which run from 50 to 100, 150, &c., 
marking every 50 fathoms. 
In all this area, whether it was warm or cold at the bottom , we 
found nearly the same sur/ace-temperature — a very curious 
fact. If we went north it was a little less, and if south a little 
more ; but about 52 degrees was the average. We found that 
in all parts of this area the descent through the lowering of the 
thermometer in the first 150 fathoms was the same ; and in the 
warm area, when we got below 150 fathoms, there was very little 
more lowering of the temperature. You see that the line in 
the warm area continues nearly horizontal till we pass about 
500 fathoms ; but from 150 to about 500 fathoms there was 
very little lowering of the temperature, the reduction being 
from 52° at the surface to about 45° at 500 or 600 fathoms. But 
now see what takes place in the cold area. This upper line, 
which at 100 fathoms is but a little below the other, begins to 
drop rapidly, so that at 200 fathoms it is very decidedly below ; 
and then it goes down still more rapidly, so that within 100 
fathoms it dropped about 1 5 degrees ; and all the water in that 
