398 LAPSE OF TIME AS INDICATED BY CHANGE OF CLIMATE. 



ciers indicate the action of heat as much as of cold. " Cold," 

 he says, " will not produce glaciers. You may have the bit- 

 terest north-east winds here in London throughout the winter, 

 without a single flake of snow. Cold must have the fitting 

 object to operate upon, and this object the aqueous vapour 

 of the air is the direct product of heat. Let us put this 

 glacier question in another form : the latent heat of aqueous 

 vapour, at the temperature of its production in the tropics, is 

 about 1000 Fahr., for the latent heat augments as the tem- 

 perature of evaporation descends. A pound of water thus 

 vaporized at the equator, has absorbed one thousand times 

 the quantity of heat which would raise a pound of the liquid 



one degree in temperature It is perfectly manifest that 



by weakening the sun's action, either through a defect of 

 emission, or by the steeping of the entire solar system in space 

 of a low temperature, we should be cutting off the glaciers at 

 their source." 



Professor Frankland has even gone so far as to express the 

 opinion that " the sole cause of the phenomena of the glacial 

 epoch was a higher temperature of the ocean than that which 

 obtains at present,"* having no doubt overlooked the fact 

 that the fauna of the sea, as well as of the land, had an Arctic 

 character. 



Secondly. Admitting the proper motion of the sun, it has 

 been suggested that we may have recently passed from a 

 colder into a warmer region of space. 



I must refer to Mr. Hopkins' memoir for his objections to 

 this suggestion ; they certainly appear to " render the theory 

 utterly inapplicable to the explanation of the changes of tem- 

 perature at the more recent geological epochs." 



This hypothesis, moreover, is liable to the same fatal objec- 

 tion as the first. To produce snow requires both heat and 

 cold ; the first to evaporate, the second to condense. In fact, 



* Phil. Mag. 1864, p. 328. 



