1230 president's address. 



Then again the occurrence of numerous remains of crocodiles 

 (reptiles which are now extinct in the valley of the Darling) at 

 Cuddie Springs on the flat country, 15 miles south of the Darling, 

 and far from other watercourses, points to a time when abundance 

 of water or swampy marshes existed over that now dry country. 



Professor Ralph Tate, of the Adelaide University, is also of 

 opinion, from the distribution of the Diprotodon, that the 

 Pleistocene was a period of great rainfall. 



As to the cause of this interesting pluvial period over a large 

 portion of the Southern Hemisphere — for its elFects have also been 

 observed in New Zealand, South America and South Africa — I 

 will state briefly some of the theories which have been put forward 

 upon the subject. 



We know that the Pleistocene deposits &c., just described, bear 

 the same relation to the present physical features, as do those of 

 the so called " Glacial Period " of the Northern Hemisphere ; and 

 it has been asserted that during the glaciation of portions of the 

 latter, a more humid climate than the present must have pi'evailed 

 in the Southern Hemisphere — an assertion which the geological 

 facts above mentioned unquestionably favor. Various causes of the 

 Glacial Pei'iod have been suggested ; but the views advanced by Dr. 

 Croll, Dr. Geikie, Professor Ramsay, Mr. A. R. Wallace, and some 

 others, have received much support. These eminent authorities 

 have suggested " that the combined eSect of the precession of the 

 equinoxes and of the excentricity of the earth's orbit" ; together 

 with " changes in the disti'ibution of land and water " are sufficient 

 to produce the phenomena observed. 



Owing to the precession of the equinoxes the inclination of the 

 earth's axis towards the sun is reversed every 10,500 years and it 

 happens that whichever hemisphere is turned from the sun when 

 the earth is in aphelion during the period of great excentricity 

 which, according to Dr. Oroll, lasted for 160,000 years ending about 

 80,000 years ago, the winter of that hemisphere is so long and cold 

 as to induce a lai'ge accumulation of snow and ice upon high lands 

 situated within regions of great precipitation : at the same time 

 the opposite hemisphere would experience equally long and cool 



