996 
THE VOYAGE OF H.M.S. CHALLENGER. 
that the bottom water at these high latitudes may have a temperature which is more nearly 
that of the surface than that of the intermediate warm layers. No. 414 and the three 
samples from the South Atlantic agree in all points very closely with one another ; the 
oxygen percentage, however, 28 ‘42, is decidedly higher than the average of the South 
Atlantic waters, 25 '81, consequently the absolute amount of oxygen is also higher and the 
oxygen deficiency less. Judging from the amount of nitrogen, the temperature at which 
these waters had been exposed to the atmosphere would be from 2° to 4° C., or probably 
lower. In all these bottom writers from the Antarctic and South Atlantic Oceans there is 
considerable uniformity in the composition of the gases ; in examining the waters of the 
North Pacific more irregularity is found. The oxygen percentage is very low, being 
generally under 20. The carbonic acid which is given off on boiling in vacuo is very 
high, over 10 c.c., and the amount of carbonic acid eliminable by distillation with chloride 
of barium varies much. Except in the case of No. 771 the amount of nitrogen is 
high, and indicates a low temperature of exposure to the atmosphere, while the deficiency 
of oxygen and the excess of carbonic acid indicate a prolonged seclusion from its 
influence. 
Intermediate Waters . — At great depths the gases from intermediate waters resemble 
those from bottom waters of the same locality. In the North Pacific the water 
No. 1001 has by far the lowest oxygen percentage, 3‘84, and the amount of carbonic 
acid in the gas tube is actually less than the “ oxygen deficiency.” No. 1009, on 
the other hand, is a deep water with abnormally high oxygen percentage, and 
No. 1269 a similar one from the South Pacific. Generally, however, in the Pacific 
Ocean the water at depths of from 100 to 500 fathoms above the bottom contain from 
20 to 22 per cent, of oxygen. No. 1532 is from 1400 fathoms in the South Atlantic, 
and No. 1645 from 1500 fathoms under the Equator in the same ocean. The difference 
in the oxygen percentage is very striking. The water from the South Atlantic 
contains 27'54, wdiile that from the Equator contains only 13‘24, per cent, of oxygen. 
This is a phenomenon which repeats itself at more moderate depths. The w 7 ater of higher 
latitudes contains a greater percentage of oxygen than that of lower latitudes at the 
same depth, and it is especially observable in the case of waters from near the Equator. 
It is not particularly observable at 800 and 400 fathoms, but at 300, 200, and 100 
fathoms it is remarkable. In equatorial latitudes the surface has usually a lower salinity 
than the water at 50 or 100 fathoms below it, which impedes vertical circulation; 
it is also largely drawn away, forming the Equatorial Currents, and is to a certain extent 
replaced by water from greater depths, already to some extent impoverished as regards 
oxygen. When this water has risen to within 300 fathoms of the surface it enters a 
region where life is more abundant than at greater depths, and where, consequently, 
there is an increased consumption of oxygen. In the table there are two equatorial 
waters, Nos. 1661 and 1672, from 300 fathoms, and one, No. 1633, from 100 fathoms from 
