CHAP, vin.] THE CAUSES OF GLACIAL EPOCHS. 



157 



staojes of the glacial epoch, when alternations of warmer and 

 colder periods would be caused by winter occurring in perihelion 

 or aphelion. If, however, as we maintain, no such alternations 

 occurred when the excentricity was near its maximum, then the 

 ice would accumulate in the southern hemisphere at the same 

 time as in the northern, unless changed geographical conditions, 

 of which we have no evidence whatever, prevented such accu- 

 mulations. That there was such a greater accumulation of ice 

 is shown by the traces of ancient glaciers in the Southern Andes 

 and in New Zealand, and also, according to several writers, in 

 South Africa ; and the indications in all these localities point 

 to a period so recent that it must almost certainly have been 

 contemporaneous with the glacial period of the northern hemi- 

 sphere.^ This greater accumulation of ice in both hemispheres 



1 The recent extensive glaciation of New Zealand is generally imputed by 

 the local geologists to a greater elevation of the land ; but I cannot help 

 believing that the high phase of excentricity which caused our own glacial 

 epoch was at all events an assisting cause. This is rendered more pro- 

 bable if taken in connection with the following very definite statement of 

 glacial markings in South Africa. Captain Aylward in his Transvaal of 

 To-day (p. 171) says : — "It will be interesting to geologists and others to 

 learn that the entire country, from the summits of the Quathlamba to the 

 junction of the Vaal and Orange rivers, shows marks of having been swept 

 over, and that at no very distant period, by vast masses of ice from east to 

 west. The striations are plainly visible, scarring the older rocks, and 

 marking the hill-sides — getting lower and lower and less visible as, descend- 

 ing from the mountains, the kopjies (small hills) stand wider apart ; but 

 wherever the hills narrow towards each other, again showing how the vast 

 ice-fields were checked, thrown up, and raised against their eastern 

 extremities." 



This passage is evidently written by a person familiar with the phe- 

 nomena of glaciation, and as Captain Aylward's preface is dated from 

 Edinburgh, he has probably seen similar markings in Scotland. The 

 country described consists of the most extensive and lofty plateau in South 

 Africa, rising to a mountain knot with peaks more than 10,000 feet high, 

 thus offering an appropriate area for the condensation of vapour and the 

 accumulation of snow. At present, however, the mountains do not reach 

 the snow-line, and there is no proof that they have been much higher in 

 recent times, since the coast of Natal is now said to be rising. It is evi- 

 dent that no slight elevation would now lead to the accumulation of snow 

 and ice in these mountains, situated as they are between 27° and 30° S. Lat. ; 

 since the Andes, which in 32° S. Lat. reach 23,300 feet high, and in 28° 



