The Geographical Journal (Journal of the Royal Geographical Society): Volume XII, No. 2 [‎260v] (23/154)

114 THE ANNUAL RANGE OF TEMPERATURE IN THE SURFACE WATERS OF THE
the strain of contraction, they split, and throw off sharp angular frag
ments from a few ounces to 100 or 200 lbs. in weight." Cold rain falling
on these sun-heated rocks produces a similar effect.f At Atacama, in
South America, a range of temperature amounting to 91° Fahr. has been
recorded in four hours.J
The annual range of temperature is likewise very great at some
places on the land-surfaces. At Werkojansk, in Siberia, the range of
temperature between the mean of the coldest month and the mean of the
warmest month is 120° Fahr.; and at this place, in February 1892, the
temperature fell to - 93 0, 6 Fahr., being absolutely the lowest temperature
of the air hitherto recorded. The extreme range of temperature of the
air which may be found upon the land-surfaces as a whole, as distinct
from the daily or annual range at any one spot, is known to exceed
220° Fahr.
When we turn to a consideration of the changes of temperature
Avhich occur in the surface waters of the ocean, it is found that these
are much less rapid, and that the daily and annual range at any one
spot, and the extreme range of temperature from equator to pole, are
all very much less than on the land-surfaces. This result is due 1o the
great thermal capacity of water, and to the fact that most of the light
and heat rays are absorbed on passing through the surface-layers of the
water. The high specific heat of water precludes such a rapid rise or
fall of temperature as takes place on land. When the temperature of
the water is raised, evaporation tends to check the rapidity of the rise;
when the temperature falls, condensation of the superincumbent vapour
checks the rapidity of the fall, and, when a low temperature is reached,
freezing sets in, again retarding the fall.
The mean daily range of temperature in the surface-waters of the
North Atlantic, as determined from the Challenger observations, made
on 126 days from March to August, 1873, and in April and May,
1876 (mean lat. 30° N., mean long. 42° W.), was only 0 o, 8 Fahr.; while
the amplitude of the daily variation in the temperature of the air over
the sea on the same 126 days was 3°*21 Fahr., or four times greater
than that of the sea over which it lies.§ During this time the Chal
lenger was near land on 76 days, and on these days the diurnal variation
was 4 0 -38 Fahr., thus showing a larger range in the temperature of
the air when near land than when out in the open sea. An examination
of the temperatures taken by the Challenger in other parts of the globe
renders it highly probable that nowhere in the open ocean does the * * * §
* Livingstone, ‘ Zambesi,’pp 492,516. London: 1865.
f Stanley, Proc. R. G. S., vol. xx. p. 142, 1876.
X Viz. from 7° Fahr. at 7 a.ra. to 98° Fahr. at 11 a.m. (J. Harding, Juur. R.G.S.,
1877, p. 252).
§ See Buchan in Challenger Report: Narrative, vol. i. pp. 998, 999, 1885; also his
“Report on Atmospheric Circulation,” Phys. Chem. Chall. Exp., part v. pp. 4-8, 1889.