102 Dr. J. Croll on the Physical Theory 



long ages of successive snowfalls. As layer after layer, con- 

 verted into ice, was being heaped upon it year by year, the 

 mass would gradually sink till it rested on the sea-bottom "*. 

 After this it would assume all the characteristics of continental 

 ice. In fact we have a condition of things exactly similar in 

 the North Sea during the height of the glacial epoch (see 

 ' Climate and Time/ p. 449). 



If such be the condition of the antarctic ice, we can readily 

 understand how it might all soon disappear under the influ- 

 ence which would be brought to bear upon it were the eccen- 

 tricity high and the southern winter solstice in perihelion. 

 The warm and equable conditions of climate which would then 

 prevail, and the enormous quantity of intertropical water 

 carried into the Southern Ocean, would soon produce a melting 

 of the ice. Layer after layer would disappear off the surface, 

 and as soon as the weight of the sheet became less than that 

 of the water which it had displaced, the sheet would float. 

 After this it would no doubt shortly break up and become 

 dispersed. 



Other Causes than Antarctic Ice affecting the Northward- 

 flowing Currents. — If we consider the effect which the present 

 amount of eccentricity, small as it is, has on the climatic 

 condition of some parts of the southern hemisphere, we shall 

 readily understand how, during the glacial epoch, the warm 

 water of this hemisphere may have been impelled northward, 

 even independently of the influence of the Antarctic ice. In 

 order to show the present effect of eccentricity on climate I 

 cannot do better than quote Mr. Wallace's own words on the 

 subject. Referring to its effects on south temperate America, 

 he says: — 



" Those persons who still doubt the effect of winter in aphelion 

 with a high degree of eccentricity in producing glaciation, should 



* In this opinion I am glad to find that Sir Joseph to a certain extent 

 concurs, for in a letter to me on the subject he says : — " I cannot doubt but 

 that the icebergs have originated from the ice of the great southern barrier; 

 and what I suspect is that much of this barrier-ice originated in pack-ice 

 over very shallow bays, increased by successive snowfalls. The quantity 

 of snow that falls in summer is enormous south of latitude 50°-60°. Cer- 

 tainly it fell on half the days of each summer month during the three 

 seasons we spent in those seas, and I think in one month snow fell every 

 day. There is no summer melting of snow and ice in the Antarctic as 

 there is in the Arctic regions. It is the only region known to me where 

 there is perpetual snow on land at sea-level. " 



Now if the snow which falls in the Antarctic regions at the sea-level 

 does not all melt, but some of it remains year by year, then permanent 

 ice formed at the sea-level, whether it be on frozen pack or on the ground, 

 must be a necessary consequence. If this be so, it cannot be true, as Mr. 

 Wallace affirms, that there is no permanent ice formed but on high land. 



