PRESENT STATUS OF SOLAR HYPOTHESIS 491 



of the way toward a Glacial period. To take a concrete example, the 

 Ehone glacier is now, according to Geikie, barely 6 miles long; the foot 

 of the ice stands at an altitude of 5,780 feet, and the surface near the 

 head of the glacier is 10,200 feet above the sea. During the period of 

 maximum glaciation the glacier was 240 miles longer than now; its foot 

 stood about 4,700 feet below the present level, and the surface in the 

 upper portions was 1,400 feet higher than today. It seems fair to assume 

 that the results of a small change of mean temperature would be propor- 

 tional to those of large changes. If this be so, the difference of 0.26° C, 

 which Newcomb finds between sun-spot maxima and minima, ought to 

 produce a change in the ice equal to about 4 per cent — that is, one twenty- 

 fourth — of the change since the height of the last Glacial epoch. In that 

 case, if the form of its valley were favorable, the Rhone glacier might 

 l)ecome 10 miles longer than it now is, or if the gradient of its valley 

 bottom be assumed as uniform it might descend to a level 180 feet below 

 tliat of the present ice-foot, or it might increase 56 feet in thickness. 

 The exact nature of the change in the glacier and its exact dimensions 

 would depend, of course, on the topography of the Rhone Valley and on 

 the relation of precipitation to temperature, winds, and other meteoro- 

 logical phenomena. The figures which have just been given, however, 

 show the order of magnitude of the results which might be expected from 

 a lowering of the mean annual temperature of the earth to the extent of 

 0.26° C, provided the change were permanent rather than temporan^ 

 A change of temperature capable of producing such results, or even re- 

 sults half as great, would scarcely seem to be too small to produce "any 

 important effect on meteorological phenomena." The truth of Newcomb's 

 conclusion appears to be at least an open question. 



The other point which Newcomb has failed to consider, namely, the 

 possibility of a change in the distribution of terrestrial temperature with- 

 out a corresponding change in the mean temperature of the earth as a 

 whole, will be taken up later. It is closely allied to another objection to 

 the ordinary form of the solar hypothesis, namety, the improbability that 

 the mean temperature of the sun can change so rapidly as to cause our 

 terrestrial changes. Both of these matters will be discussed later, after 

 we have considered the question of cyclonic storms. 



Apparent contradictions between temperature changes in different 

 parts of the world. — Leaving now the direct effects of temperature, let us 

 consider the effect of movements of the air on temperature and on our 

 view of the probability that solar changes are the cause of the variations 

 of terrestrial climate. In the opinion of meteorologists, the greatest ob- 

 jection to the solar hypothesis is probably the numerous apparent con- 



