TEMPERATURE AND MOVEMENTS OF THE DEEP SEA. 1 27 
down to its freezing point ; the more it is cooled the heavier it 
becomes, because its bulk diminishes ; it therefore sinks in 
proportion to its degree of coldness ; and in this manner it is 
that the coldest water nearly always comes to be at the bottom. 
This has a most important relation to the doctrine of Sub- 
marine Climate. I have shown you here a sort of little compact 
pocket edition of a set of phenomena, which, as I am now going 
to explain, probably prevails over the whole of our great Oceans. 
In our soundings a few months ago on the coast of Spain and 
Portugal, we came upon this fact ; the surface temperature was 
very high, about 65 degrees ; in the first 100 fathoms we lost 
.about 10 degrees of this, which we may call the swper-heating 
of the surface, produced by the powerful rays of the midsummer 
sun. Then the temperature from a depth of 100 fathoms down 
to 800 lowered very slowly, just as it does in the “ warm area ; ” 
so that at 800 fathoms it only got down to 49 degrees. But in 
the next 200. fathoms, between 800 and 1,000, there was a loss 
of 9 degrees, the temperature falling to 40 ; in another 100 
fathoms, it fell another degree ; and over the deeper soundings 
which we took in the previous year, extending down to 2,435 
fathoms, or nearly Three miles — a depth about equal to the 
height of Mont Blanc — we got a temperature as low as 361- 
degrees ; and still lower temperatures have been obtained 
elsewhere, even near the Equator. The recent temperature- 
soundings made by Commander Chimmo with the 66 protected ” 
thermometers, in Lat. 3° S. and Long. 95° E., have given 35°*2 
as the bottom-temperature at 1,806 fathoms, and 33°*6 at 2,306 
fathoms. Here, then, you see we have in our great Oceans a 
condition just comparable with that which we found in the 
Lightning Channel : first we have an upper stratum of warm 
water ; then we have what I have designated a “ stratum of in- 
termixture;” but below 1,000 fathoms, the water ranges from 
39° nearly down to freezing point. Near the Pole it is quite 
down to freezing point ; but when it is nearer the Equator, 
where it has had a long way to flow from the Pole, it will have 
acquired a certain slight degree of warmth ; but still, you see, 
the finding a temperature of 33 or 35 degrees under the Equator, 
shows clearly that that water must have come from one or 
other of the Poles. 
Let us now inquire what account can be given of this 
remarkable phenomenon. Here we have in the deep Oceanic 
basins this layer of water extending more than a mile deep — 
water which must have been derived from the Polar area. 
What account can we give of it ? How does it come to be 
there ? and how does it come to retain its low temperature ? 
Now I think it may be said with perfect certainty, that it could 
not long retain its low temperature unless it was continually 
