E. P. Culverwell— Theory of the Ice Age. 61 



are those of the greatest mean annual range. We are, therefore, 

 entitled to infer that the effect of such a change in the eccentricity 

 as we have supposed would be to increase the range, lower the 

 temperature of the hemisphere, and thus induce the Glacial period." 

 How are we to discuss such an assertion? It amounts to this, 

 that loithout examining what the alleged connection betiveen annual 

 temperature and annual range is, and loithout any previous attempt 

 to ascertain what temperature is necessary to bring about an Ice Age 

 we are "entitled to infer" that a range of 28° F. in Great Britain 

 would mduce the Glacial period ! So far from that being the case, 

 the most cursory examination of the far greater ranges of tempera- 

 ture m non-glaciated regions at present seems to entitle us to infer 

 that the supposed increase of range would be quite powerless to 

 eflect the desired, or indeed, any very marked change in climate. 



ihe other quantitative statement is to be found on p. 105, where 

 still working on the basis of the 63 and 37, Ball calculates that in 

 the Glacial winter there would be a deficiency of 7 per cent, in the 

 average daily supply of sun-heat as compared with our present 

 winter supply, the unit being the average annual daily sun-heat. 

 As the unit, according to Ball's supposition, keeps Great Britain 

 d5U degrees above the natural zero, this might be supposed (accord- 

 ing to the erroneous theory adopted by Ball and Croll alike) to 

 produce a lowering of 24-5° F. in the winter temperature of Great 

 Britain. Ball does not here make the calculation, but I make it on 

 his principles in order to show how small is the result obtained by 

 Ball as compared with that of Croll, who gets a lowerino- of 45-3° F 

 in the winter temperature of Great Britain. Hence, "^o far from 

 Ball being correct in thinking that if Croll had known his form 

 of the purely astronomical portion of the theory, he would not have 

 considered the alteration of the Gulf Stream a necessary adjunct 

 It would seem as if Croll would then have wanted a second Gulf 

 fetream to help him for the 45-3 minus 245 degrees of refrigeration 

 be would have to abandon. 



I now pass to another point. It was long ago stated by Tyndall 

 that great ^ heat to produce evaporation was as necessary in giving 

 rise to a Glacial age as great cold to produce condensation. After 

 agreeing with this. Ball states that the astronomical theory shows 

 where to look for the necessary heat. He points out correctly that 

 the annual quantity of heat received by the whole earth is not 

 lessened, and he continues (p. 109)-" If, therefore, the glaciated 

 hemisphere received during its winter a deficient supply of heat 

 to which the glaciation owes its origin, the defect of heat upon this 

 hemisphere loill have to be compensated for elseichere. More favoured 

 regions of the globe will accordingly enjoy a more copious supply 

 ot sunbeams, and thus those volumes of aqueous vapour will be 

 provided which, put in circulation by the winds, are deposited in 

 the form of snow when the ice-sheets are growing." Here is an 

 oversight, not unlike that of Herschel, to which reference has been 

 made. The sentence I have italicised should read, "the defect of 

 winter heat on this hemisphere is compensated for," not elsewhere 



