their temperature is augmented 3 or 4 degrees by the contact of strata
less cold. If water in cooling continued to condense uniformly to the
freezing point, there would be found, in very deep lakes and basins
having no communication with each other (whatever the latitude of the
place), a stratum of water, the temperature of which would be nearly
equal to the maximum of refrigeration above the freezing point, which
the lower regions of the ambient atmosphere annually attain. Hence it
is probable, that, in the plains of the torrid zone, or in the valleys
but little elevated, the mean heat of which is from 25.5 to 27
degrees, the temperature of the bottom of the lakes can never be below
21 or 22 degrees. If in the same zone the ocean contain at depths of
seven or eight hundred fathoms, water the temperature of which is at 7
degrees, that is to say, twelve or thirteen degrees colder than the
maximum of the heat* of the equinoctial atmosphere over the sea, I
think it must be considered as a direct proof of a submarine current,
carrying the waters of the pole towards the equator. (* It is almost
superfluous to observe that I am considering here only that part of
the atmosphere lying on the ocean between 10 degrees north and 10
degrees south latitude. Towards the northern limits of the torrid
zone, in latitude 23 degrees, whither the north winds bring with an
extreme rapidity the cold air of Canada, the thermometer falls at sea
as low as 16 degrees, and even lower.) We will not here solve the
delicate problem, as to the manner in which, within the tropics and in
the temperate zone, (for example, in the Caribbean Sea and in the
lakes of Switzerland,) these inferior strata of water, cooled to 4 or
7 degrees, act upon the temperature of the stony strata of the globe
which they cover; and how these same strata, the primitive temperature
of which is, within the tropics, 27 degrees, and at the lake of Geneva
10 degrees, react upon the half-frozen waters at the bottom of the
lakes, and of the equinoctial ocean. These questions are of the