66 



is, so far as I am aware, new in application to this case, 

 whereby it is not only probable, but very possible, that our 

 comparatively recent drifts, whicb occupy considerable tracts 

 of the lower situated lands of South Australia were laid 

 down. 



The great philosopher, Laplace, was the first to demonstrate 

 the fluctuation of sea level. In short, he was the first to 

 advance that the level of the ocean was regulated entirely by 

 transference — on a grand scale — of solid matter from one part 

 of the earth's surface to another. The same theory was revived 

 about ten or twelve years ago by Dr. Croll, of the Geological 

 Survey of Scotland, and subsequently accepted by Sir William 

 Thomson, F.E.S. It would be presuming too much, on my 

 part, to enter here in detail upon matters with which a majority 

 of members present are fully acquainted. Allow me, however, 

 to state this much that Dr. Croll and Sir "William have 

 penetrated into the mystery so far as to enable them to advance 

 the opinion that our earth undergoes long secular changes of 

 summer and winter, brought round by some natural law, just 

 as truly and surely as that regulating the change of our annual 

 summers and winters. 



Treating on this subject, Dr. Croll expresses himself in the 

 following words : — "When the eccentricity of the earth's orbit 

 is at a high value, and the northern winter solstice is in 

 perihelion, agencies are brought into operation which make the 

 south-east trade winds stronger than the north-east, and compel 

 them to blow over upon the northern hemisphere, as far 

 probably as the Tropic of Cancer. The result is that all the 

 great equatorial currents of the ocean are impelled into the 

 northern hemisphere, which thus, in consequence of the 

 immense accumulation of warm water, has its temperature 

 raised, and snow and ice to a great extent must then disappear 

 from the Arctic regions. When the precession of the equinoxes 

 brings round the winter solstice to aphelion, the condition of 

 things on the two hemispheres is reversed and the north-east 

 trades then blow over upon the southern hemisphere carrying 

 the great equatorial currents along with them. The warm 

 water being thus wholly withdrawn from the northern hemis- 

 phere, its temperature sinks enormously, and snow and ice 

 be<nn to accumulate in temperate regions. The amount of 

 precipitation in the form of snow in temperate regions is at 

 the same time enormously increased by the excess of the 

 evaporation in low latitudes resulting from the nearness of 

 the sun in perihelion during summer." — (Geological Magazine, 

 Decade n., vol. v., p. 397.) 



Dr. Croll sums up his argument as follows : — " The final 

 result to which we are, therefore, led is that those warm and 



