TRANSACTIONS OF SECTION C. — PRESIDENTIAL ADDRESS. 403 



SECTION C— GEOLOGY. 



President of the Section: — Professor Grenville A. J. Gole, 



F.G.S., M.E.I. A. 



WEDNESDAY, SEPTEMBER 8. 

 The President delivered the following Address : — 



In his Address to this Section at Sydney in 1914, my predecessor,^ Sir Thomas 

 Holland, dealt with the problem of isostatic balance in the earth's crust, and 

 with tlie relation of crust-movements to what Ampferer has styled the Unter- 

 grund. Such broad questions must appeal to all geologists. Without move- 

 ments of the surface, the ocean-depths would become diminished by infilling 

 from the denuded lands, and the water would spread, by a general trans- 

 gression, across the shores of worn-down continents. Rivers would become 

 reduced, both in length and volume, and there would be a marked diminution in 

 the salts carried to the sea. Molluscan life would probably profit by the 

 greater extent of warm and shallow waters, while the variety of animal types 

 on a given land-area would decrease before a growing equality of conditions. 

 Volcanic action, so commonly the accompaniment of large displacements, would 

 no longer find definite lines of outbreak, and a number of interesting petro- 

 graphic types might remain unseen or even undifferentiated in the quiescent 

 cauldrons of the crust. Students of tectonics, physical geography, paleeontology, 

 and petrography are thus alike concerned with superficial warping. More than 

 this, the whole life of man, his future as much as his past, is conditioned by 

 the security or insecurity of the land on which he moves. If to-day I venture 

 to touch on some of these large aspects of our science, it will be understood 

 that tbis is not from any pride of knowledge on my part, or from any special 

 grasp of a 'theory of the earth.' The conclusion that I should prefer to 

 emphasise is that "the faithful and minute observations of the geologist, the 

 discussion of detail, the aid that he may draw from the experiments of the 

 chemist and the physicist, and, above all, the frequent conference with others in 

 the field, all tend to an understanding of human surroundings on this strange 

 rotating globe. The globe is still strange to us, because its vast interior is 

 unseen ; and we are apt to speculate about the stars, when the behaviour of the 

 ground beneath us concerns us far more nearly. 



Changes in the relative Proportions of Sea and Land. 



The geologist has long been accustomed to regard the crust beneath his feet 

 as subject to changes which are immeasurably slow in comparison with the 

 duration of his personal life. Since the days of Lyell, the processes of recon- 

 struction have seemed to us as mild and lengthy as are the processes of decay. 

 Tt is true that even the latter processes display vigorous tendencies in the form 

 of landslides and the paroxysmic eruptions of volcanoes, while earthquakes at 

 times are accompanied by visible displacements of the crust, such' as that which, 

 at Yakutat Bay, in .1899, raised the sea-coast as much as forty-seven feet. 



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