Geological Climatology. 
249 
its heat as rapidly as the land, it must stand at a higher tempe- 
rature than the land. The temperature of the sea must continue 
to rise till the amount of heat thrown off into space equals that 
received from the sun ; when this point is reached, equilibrium 
is established and the temperature remains stationary. But, 
owing to the greater difficulty that the sea has in getting rid 
of its heat, the mean temperature of equilibrium of the ocean 
must be higher than that of the land ; consequently the mean 
temperature of the ocean, and also of the air immediately over 
it, in tropical regions should be higher than the mean tempe- 
rature of the land and the air over it/ 
Since the publication of ' Climate and Time 3 the accuracy 
of this conclusion has been confirmed in a remarkable manner 
from more recent researches on the actual mean temperature 
of the two hemispheres, the details of which have been given 
byMr.Ferrellin his ' Meteorological Eesearches' (Washington, 
1877). It is found that them ean temperature of the northern 
or land hemisphere is higher than that of the southern or 
water hemisphere up only to about latitude 35°, and that 
beyond this latitude the mean temperature of the water 
hemisphere is the greater of the two. At latitude 40° the 
mean temperature of the southern hemisphere is l° - 4 higher 
than that of the same parallel on the northern hemisphere. 
At latitude 50° the difference amounts to 4°"4; while at latitude 
60° the mean temperature of the southern hemisphere is 
actually 6° higher than that of the northern on the same 
parallel. The mean temperatures of the two hemispheres are 
as follows : — 
Lat. ... 
0° 
10° 
20° 
30° 
40° 
50° 
60° 
70° 
80° 
Northern.. 
Southern... 
8U-1 
80-1 
o 
81-0 
78-7 
o 
77-6 
74-7 
6?6 
66-7 
o 
56-5 
57-9 
43-4 
47-8 
o 
293 
35 3 
14-4 
o 
4-5 
From the above table we see that it is only in that area 
lying between the equator and latitude 35° that the southern 
hemisphere has a lower mean temperature than the northern. 
But it is from this area that the enormous amount of heat 
transferred to the northern hemisphere is mainly derived. 
Were the transference of heat to cease, the temperature of this 
area would be very considerably raised, and that of the corre- 
sponding area on the northern hemisphere lowered. The 
result would doubtless be that the southern hemisphere down 
to the equator would then be warmer than the northern. But, 
