62 SECTIONAL ADDRESSES 



fully the profound influence exercised by those rhythmic or cataclysmic 

 earth-movements on the evolution of life is, however, only to carry the 

 inquiry a stage farther back. The vera causa still remains obscure. 

 Latterly we have witnessed efforts to explain both mountain-building 

 movements and the more widespread interchange of areas of land and 

 sea as the effects of convection currents in the earth's interior, resulting 

 from changes of density due to temperature and pressure or to mineral 

 rearrangement in the subcrustal materials : ' oft the teeming earth Is 

 with a kind of colic pinch'd and vex'd.' 



Thus we arrive once more at the necessity for an understanding of 

 the problems of physico-chemical relationships. Whether sub-crustal 

 volume-changes in minerals and rocks originate as the result of a legacy 

 from solar parentage in the form of the earth's internal heat, or of the 

 running-down of the radio-active clock, is still a matter for discussion ; 

 but there is little doubt that the effects of the atmosphere and hydrosphere 

 on the crust, in eroding a load of rock in one place and imposing newly- 

 formed sediment in another, have played their part in determining the 

 location of crustal disturbances. 



Many of the other contacts of geology are so obvious and familiar 

 that I need only refer to them briefly. Such, for example, are illustrated 

 by the intimate relationships of botany and zoology to palaeobotany 

 and palasozoology. Again, it is unnecessary to emphasise that the study 

 of either living organisms or fossil remains cannot be effective if divorced 

 from one another. Nor need one amplify the statement that the proof 

 of the reality of evolution rests with the geologist. 



In the case of geography, the connection may be through the physical 

 or the humanistic sides. Physical geography, for example, is but physical 

 geology re-named and, as a sine qua non of preliminary geographical studies, 

 its essential basis is field-work. It can only be taught effectively, there- 

 fore, by the geologist. The influence on the development of mankind of 

 the major crustal features of the earth and of scenic types is profound, 

 as also is that of the solid and superficial rocks and of the various mineral 

 resources contained in them. To mention only one example, the parti- 

 tion of Hungary, like the restoration of Alsace, suggests that if a geological 

 map did not hang on the wall at the Versailles Congress, its implications 

 were in the minds of those present. 



In the application of geological principles to the problems of civil 

 engineering we have a contact which has become increasingly close 

 during the last half-century. Indeed, it is scarcely an exaggeration to 

 say that no great engineering undertaking that involves an interference 

 with the materials and loading of the earth's crust is now promoted 

 without geological advice. Loss of life and money, as well as the possi- 

 bility of subsequent litigation, is thereby reduced to a minimum. Canal- 

 cutting, tunnelling, road and railway construction, drainage, coast-erosion, 

 mitigation of earthquake-effects, harbour-engineering, sanitation, and 

 impounding of water-supplies for either power purposes or direct utili- 

 sation all require a detailed knowledge of the geology of the locality if 

 they are to be successfully prosecuted. The recovery of underground 

 water by means of wells, boreholes, and adits has long been dependent 



