ANTARCTICA. 2cSl 



beneath and forms the margin of our Karroo, being a deposit 

 formed by th action of Permo-Carboniferous ice-sheets. 



Attempts have been made to explain these ice-ages on such 

 grounds as : — 



( i ) Changes in the amount of carbon dioxide in the atmo- 

 sphere. 



(2) Shifting of the Poles. 



(3) Amount of heat received from the sun. 



(4) Distribution of land and sea. 



(5) Existence of high land areas, etc., etc.. 



None of these theories can be regarded as proved. The 

 effect of these glaciations must have been very serious on the dis- 

 tribution of living forms, and must needs compel us to realise 

 that glaciation in the past was a factor which must be considered 

 in the distribution of living forms. 



We have, then, definite proof of vast climatic changes in 

 Antarctica, and can understand that a closer knowledge of the 

 past fauna and flora may render great assistance in the elucida- 

 tion of problems of distribution in the Southern Hemisphere. 



Before leaving Antarctica itself, I would like to refer to an 

 important and interesting point — land movements as recorded by 

 Raised Beaches. 



There is no doubt that glaciation has some time since reached 

 its maximum in Antarctica. This is evidenced by land features 

 and also by the diminution of the Great Ice Barrier. This mass 

 has been retreating inland since Ross's records were made in 

 1841. It has been found that about thirty-five miles of the mass 

 have disappeared during the seventy years in the region of 

 McMurdo Sound. This may be taken as an indication of lessen- 

 ing glaciation and less rigorous climatic conditions. 



The raised beaches which were discovered in the region of 

 Cape Barnes might reasonably be explained as an emergence or 

 recovery resulting from the lessening of the huge ice-weight after 

 maximum glaciation had been passed. 



In attempting to map in the land areas and connections of 

 the past we will be compelled to rely to a great extent on out- 

 knowledge of living and extinct life forms from the standpoint 

 of distribution. This is due to our lack of knowledge in regard 

 to earth movements, and I would here refer to an important 

 omission in our attempts to unravel the secrets of Dynamical 

 Geology — I refer to the absence of combined efforts to record 

 the exact doings of our Coast lines. 



We know that no part of our land areas can be regarded as 

 stable, and that movements of importance in regard to land 

 masses are extremely slow and imperceptible. Had we at our 

 disposal the exact records of the movements of the various Coast 

 lines of our land areas for the past two hundred years, or more 

 perhaps, we would in all possibility have a guide which might 

 enable us. in a broad way. to look more confidently and precisely 

 into the more recent past, and even to look into the future. We 



