Points in Climatology. 145 



" First. — The ground stores up heat only by the slow process of 

 conduction, whereas water, by the mobility of its particles and its 

 transparency for heat-rays, especially those from the sun, becomes 

 heated 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." 



As just remarked, Mr. Croll substitutes a sound reason for 

 this utterly bad one, but still seems inclined to hold on to the 

 latter. The confusion of ideas which pervades it can best be 

 shown by making some attempt to put the statements into 

 quantitative language, using numbers, lengths, &c, instead of 

 the qualifying words " slow," " considerable," " rapidly," 

 " comparatively small/'' and " great." His statement would 

 then read something in this shape : — The ground stores up 

 heat only by the process of conduction which admits of only 

 10 calories per square metre being absorbed in a day, whereas 

 water, by the mobility of its particles &c, becomes heated to a 

 depth of thirty feet at the rate of 1° Fahr. per hour (day or 

 week as the case might be) . Thus only 1000 units of heat 

 are stored up in a cubic metre of earth, while 5000 units per 

 cubic meter are stored up in the ocean. 



When stated in this form, the question how hot the ocean 

 would get at the end of x days, weeks, or years under the 

 supposed law of heating, and how the number of units of heat 

 stored up respectively in the ground and the ocean would fix 

 their respective temperatures, would at once have arisen in 

 Mr. CrolPs own mind and showed him the utter failure of his 

 reasoning ; but by using instead of numbers the qualifying- 

 phrases I have quoted he confuses integral quantity of heat, 

 rate at which heat is radiated in a unit of time, heat stored 

 up, and temperature, without destroying the apparent sound- 

 ness of his argument in the mind of the uncritical reader. 



The second reason is in the following words: — 



" Second. — The air is probably heated more rapidly by contact 

 with the ground than with the ocean ; but, on the other hand, it is 

 heated far more rapidly by radiation from the ocean than from the 

 land. The aqueous vapour of the air is to a great extent diather- 

 manous to radiation from the ground, while it absorbs the rays 

 from water and thus becomes heated/*' 



Here, again, the fallacy of the reasoning will be seen by 

 giving the respective number of degrees, or any quantitative 

 statement of the rate at which the air was heated by radiation 

 from the ocean and from the land respectively. The fact I 

 suppose to be that there is no rapidity of heating in question, 

 but that the question is simply one of stationary temperature 

 Phil Mag. S. 5. Vol. 17. No. 104. Feb. 1884. L 



