584 
on the surface, the great mass of the ocean consisting of cold 
water—water of 45°, 40°, and of even a much lower tem- 
perature. Ata little over half a mile of depth in the tropics 
the water has a temperature of 40°, and at the bottom it is 
still colder—ice-cold indeed. The ooze which is dredged from 
the bottom beneath the burning sun of the equator is so cold 
that the hand cannot be held in it for any time without great 
discomfort. 
In the open ocean the temperature usually decreases with the 
depth, the coldest water being found at the bottom; but some- 
times there are limited areas where the temperature remains 
uniform for a mile or half a mile above the bottom. This has 
been shown to depend on the existence of barriers to free circu- 
lation, which exist on the floor of the ocean, and cause in a 
measure a resemblance to the conditions which are so marked in 
many partially enclosed seas, shut off by submarine barriers 
from general oceanic circulation, where the temperature is uni- 
form, it may be, from a few fathoms below the surface to the 
bottom—for instance, in the Mediterranean and Seas of the 
Malayan Archipelago. 
The low temperature of deep ocean water was acquired at the 
surface in high latitudes, chiefly in the high latitudes of the 
southern hemisphere. The salt warm water of the tropical 
regions, which is driven in relatively rapid currents along the 
eastern shores of South America, Africa, and Australia by the 
action of the prevailing winds, on reaching a southern latitude 
of 50° or 55° sinks on being cooled, and spreads over the 
floor of the ocean. A similar circulation takes place in the 
northern hemisphere, though modified in many ways by the 
peculiar configuration of the land: for instance, it is almost 
certain that the cold water at a temperature of 30° F., which 
occupies the deeper part of the Norwegian Sea beyond the 
Wyville-Thomson Ridge, is the dense surface water of the 
Atlantic, which becomes cold and sinks as it passes northward 
in the extension of the Gulf Stream. Again, the relatively low 
temperature found on the eastern coasts of Africa and America 
seems largely due to the cold deep water which is drawn up to 
supply the place of the warm surface water driven forward by 
the trade winds. 
While surface currents, both warm and cold, have at times 
considerable velocities, there is no evidence that rapid currents 
exist anywhere in the great deeps, on the contrary, the move- 
ments must be extremely slow and massive in character ; the 
only exception seems to be on the crests of some ridges at 
moderate depths between volcanic islands or other similarly 
situated places. 
Through the constant circulation in the ocean the gases of the 
atmosphere, which are everywhere absorbed at the surface of 
the sea according to the known laws of gas absorption, are 
borne down and thus enable myriads of living organisms to 
carry on their existence at all depths. The nitrogen remains at 
all times and places nearly constant, but frequently the propor- 
tion of oxygen is much reduced in deep water, owing to the 
processes of oxidation and respiration which are there going on. 
The absorbed carbonic acid plays a most important and 
intricate 7d/e in the economy of the ocean, owing to its tendency 
to reduce normal carbonate of lime and magnesia to solution in 
the form of bicarbonate ; and to the rapid interchanges to which 
it is subject in consequence of vital processes. It probably re- 
ceives large additions from the bottom of the ocean, as an after- 
product of volcanic eruptions, and through the respiration of 
animals. 
It is often supposed that hydrochemical actions go on with 
much greater activity in the deep sea where there may be a pressure 
of four or five tons on the square inch, but, while it would be 
convenient to assume it, there is no sufficient evidence that such 
is the case. The disintegrations, decompositions, and depo- 
sitions which take place in the deposits are all similar to those 
which take place in shallow water or on land, and any chemical 
peculiarities occurring in inorganic or organic substances in great 
depths are probably due chiefly to the low temperature, almost 
perfect stillness, and the absence of light: for, although it may be 
admitted that some rays descend to much greater depths in the 
sea than is usually supposed, yet we must at present believe that 
none of them reach the greatest depths. The absorbed gases 
are probably but little affected by the great pressure of the 
superincumbent water, for in this connection it should be re- 
membered that water is but little compressible ; any substance 
which will sink to the bottom of a tumbler of water will in time 
sink to the bottom of the deepest ocean; this is true at least 
NATURE 
[ Oct. 15, 1885 
for all substances which are more compressible than water 
itself. The compressibility of water cannot, however, be 
neglected in oceanographical questions. In very great depths 
the lower layers are considerably compressed ; for instance, in 
an ocean five miles deep, were the action of gravity suddenly 
to cease, the water would rise about 500 feet above its present 
level from expansion, a height sufficient to submerge nearly all 
the habitable land of the globe. 
It remains to mention the investigations, which have recently 
been made, as to the change of level of the ocean, owing to the 
attraction of the masses of continental or other land—such, for 
instance, as that of the Himalayas for the water of the ocean to 
the south, by which the level of the Southern Indian Ocean is 
lowered some hundred feet ; the bearing of this on the apparent 
elevation or submergence of land along coast-lines is evident, 
for the level of the sea, to which we refer all heights and 
depths, cannot be regarded as much more stable than the solid 
land itself. 
(Zo be continued.) 
NEW PROCESS OF LIQUEFYING OXYGEN * 
LIQUID ethylene, the preparation and use of which I have 
already explained, shows, at its boiling-point under the 
pressure of the atmosphere, atemperature of at least — 103° C., 
only some 10” from the critical temperature of oxygen (— 113° C.). 
It is understood how in the expansion of compressed and cooled 
Fic. 1. 
oxygen in the boiling ethylene the lowering of the temperature 
resulting from the expansion enabled me to establish ‘‘a 
tumultuous ebullition continuing an appreciable time.” In 
1 From the Journal de Physique. By M. L. Cailletet. The illustrations 
have been kindly lent by MM. Ducretet et Cie, the manufacturers of M. 
Cailletet’s apparatus. 
