794 REPORT— 1892. 



Section E.— GEOGRAPHY. 



President or thb Section— Professor James Geikie, LL.D., D.C.L., F.R.S., 



F.R.S.E., F.G.S. 



THURSDAY, AUGUST 4. 



The President delivered the following address : — 



Amongst the many questions upon which of late years light has been thrown by 

 deep-sea exploration and geological research, not the least interesting is that of 

 the geographical development of coast-lines. How is the existing distribution of 

 land and water to be accounted for ? Are the revolutions in the relative position 

 of land and sea, to which the geological record bears witness, due to movements 

 of the earth's crust or of the hydrosphere ? Why are coast-lines in some regions 

 extremely regular, while elsewhere they are much indented ? About 150 years 

 ago the prevalent belief was that ancient sea-margins indicated a formerly higher 

 ocean-level. Such was the view held by Celsius, who, from an examination of the 

 coast-lands of Sweden, attributed the retreat of the sea to a gradual drying up of 

 the latter. But this desiccation hypothesis was not accepted by Playfair, who 

 thought it much more likely that the land had risen. It was not, however, until 

 after Von Buch had visited Sweden (1806-1808), and published the results of his 

 observations, that Playfair's suggestion received much consideration. Von Buch 

 concluded that the apparent retreat of the sea was not due to a general depression 

 of the ocean-level, but to elevation of the land — a conclusion which subsequently 

 obtained the strong support of Lyell. The authority of these celebrated men 

 gained for the elevation theory more or less complete assent, and for many years 

 it has been the orthodox belief of geologists that the ancient sea-margins of Sweden 

 and other lands have resulted from vertical movements of the crust. It has long 

 been admitted, however, that highly flexed and disturbed .strata require some other 

 explanation. Obviously such structures are the result of lateral compression and 

 crumpling. Hence geologists have maintained that the mysterious subterranean 

 forces have affected the crust in different ways. Mountain-ranges, they conceive, 

 are ridged up by tangential thrusts and compression, while vast continental areas 

 slowly rise and fall, with little or no disturbance of the strata. From this point 

 of view it is the lithosphere that is imstable, all changes in the relative level of 

 land and sea being due to crustal movements. Of late years, however, Traut- 

 schold and others have begun to doubt whether this theory is wholly true, and 

 to maintain that the sea-level may have changed without reference to move- 

 ments of the lithosphere. Thus Hilber has suggested that sinking of the sea- 

 level may be due, in part at least, to absorption, while Schmick believes that 

 the apparent elevation and depression of continental areas are reaUy the results 

 of grand secidar movements of the ocean. The sea, according to him, periodi- 

 cally attains a high level in each hemisphere alternately, the waters being at pre- 

 sent heaped up in the southern hemisphere. Professor Suess, again, believing 

 that in equatorial regions the sea is, upon the whole, gaining on the land, while 



