318 Terrestrial Climate as influenced by the 
without greatly adding to the stock of our knowledge.” While 
the feeble conducting power of the solid portion of the earth’s 
coating, allows but a small portion of the sun’s heat to pass be 
neath the surface, so that whatever warmth is thus received on 
that surface during the day is readily radiated into space during 
the night, a liquid mass, similarly exposed to sunshine and sub- 
sequent nocturnal radiation, possesses peculiar properties which 
greatly influence the differences between its thermal losses and 
gains. The most important of these properties are, (1) the ee 
capacity of water for heat, by which it gradually accumulates 
and slowly parts with whatever warmth it has received; and 
(2) the intermobility of its particles, by which exchanges of 
temperature in different parts of the liquid mass are essen 
promoted. 
_ Let us consider the effect of the sun’s rays on a globe covered 
ith water, and we shall soon perceive that a more energelt 
process than that of conduction accompanies the exchanges 
temperature between the different portions of the fluid. : 
given area, but also the depth to which the rays of heat pent 
: “ made by these 
rature, de 
pending on the latitude, the hour angle, and the sun's longit 
equally heated portions of the fluid. The colder currents ures 
usually tend to flow beneath the warmer, unless at tempé ‘er 
approaching that of the maximum density of water, ane ge 
process of circulation would be established by which the 
rature acquired by the superficial strata of the water vrface. 
vapor a certain portion of the 
imparted, in the formation of clouds, to the superine 
to sink into the colder liquid which lies beneath, and ie he 
naturally tend to take its place, b ascending bo fae water 
’ e water 
: ; tface oO! ! ) 
Sidi til of evaporation would cool the SUmAc® 1 ing prow : 
ike that of radiation, it is not altogether 
# 
a 
ee, ae 
i 
