J. Croll—Geological Climatology. 253 
must be as powerful as ocean currents in tending to equalize 
the temperature of the globe.” How can this be ? 
he is about to criticise 
to prove was, not that the mean temperature of the ocean 
‘8 greater than that of the land, but that were it not for 
certain causes the mean temperature of the ocean ought to be 
steater than that of the land in equatorial regions as well as 
in temperate and arctic regions. In other words, the object of 
the chapter is to prove that the mean temperature of the 
Southern or water hemisphere is less than that of the northern 
or land hemisphere, not, as is generally supposed, because the 
former is mainly water and the latter land, but because of the 
*hormous amount of heat transferred from the former to the 
latter hemisphere by means of ocean currents ; and that were 
\t not for this transference the temperature of the water would 
exceed that of the land hemisphere. And it is in order to 
Prove this that the “four @ priori reasons” which Professor 
eweomb criticises were adduced. The first of these is as 
follows — 
First.— The ground stores up heat only by the slow process of 
Conduetion, whereas water, by the mobility of its particles and its 
ausparency for heat-rays, especially those from the sun, becomes 
eated to a considerable depth rapidly. , The quantity of heat 
stored up in the ground is thus comparatively small, while the 
quantity stored up in the ocean is great.’* 
: ese sentences are considered unworthy of criticism, Are 
: ey really so unworthy ? Let us examine them a little more 
Closely, It is in consequence of the sun’s rays being able to 
* Climate and Time,’ p. 90. 
