G'2 Proceedinfiii of the Royal Society of Victoria. 



glacier origin of whieli there can be no doubt. It is useless 

 at this stage of geological inquir_y to maintain that icebergs 

 can produce roches moutonnees. A full discussion of this 

 point may be read in Dr. Croll's " Climate and Time," 

 Geikie's " Great Ice Age," and in "The Labradoi- Coast," by 

 Dr. Packard. In connection with the upper till, though no 

 undoubted roches moutonnees have yet been met with, yet, 

 as we have seen, shattered rock surfaces below the till are 

 found, which may be said to be quite as characteristic of 

 the action of glacier-ice as a smoothed and moutonnee 

 surface. 



It now becomes a most important and interesting question 

 to determine the respective ages of the two tills. It seems 

 certain that we must look to astronomy for the explanation 

 of ice ages. Dr. Croll's celebrated theory has, until now, 

 notwithstanding considerable adverse criticism, been the 

 most satisfactory ex])lanation offeied. Recently, however, 

 Sir Robert Ball in his little work " The Cause of an Ice Age," 

 has re-stated the astronomical theory, pointing out an error 

 made by Croll. It would be beyond the scope of this 

 present paper to enter into a discussion on the cause of ice 

 ages, it will suffice to say that Sir Robert Ball has stated 

 the case with great force and clearness. The theory as it 

 now stands shows that when the astronomical conditions 

 for the production of extensive glaciation arise, then we have 

 a period during which several glacial epochs alternate with 

 genial epochs between the two hemispheres, the length of 

 each epoch being 10,500 years. The conditions for this state 

 of things then graduall}^ disappear, and do not occur again 

 till after the lapse of long ages. Sir Robert Ball says he 

 makes no attempt to state the date of the last glacial period, 

 nor to say when the next is to take place. So, according to 

 this theory, using the term "period "to embrace several 

 glacial and genial " ejwchs," we should expect to find 

 evidence of glaciation in both hemispheres during the same 

 period, though not necessarily to the same extent, for of 

 course the astronomical conditions for glaciation are liable 

 to considerable modification by the existing distribution of 

 land and sea, and the elevation of mountain chains. 



Now, taking the case of our lower till first, we have seen 

 that it is overlaid (apparently unconformably) by rocks 

 which have been assigned to Lower Triassic age. In the 

 Permian Period in the Northern Hemisphere, there are clear 

 indications of a glacial epoch or epochs. In England, Dr. 



