50 OBSERVATIONS ON THE CAUSES OF ELEVATION, ETC. 



discussing any one view to summarise briefly the principal 

 hypotheses whkh have gained the greatest acceptance among 

 scientific observers generally. The evidences for the vast 

 extent of movements of elevation and subsidence, past and 

 present, are so well established that I need only confine my 

 attention to the leading theories concerned in their 

 causation. 



Formation of Continental Areas and Ocean Basins. 



Assuming that at first the earth was a heated sphere 

 around which the existing waters of ocean seas and rivers 

 were gathered in the form of a gaseous envelope, we are 

 led to conclude that the radiation of heat, immediately prior 

 to the cooling and consequent condensation of water vapours, 

 would gradually tend to form a solid crust. The question 

 of importance at- this stage is : Was the surface matter 

 homogeneous and smooth immediately before and after it 

 hardened into a crust, or was it heterogeneous, containing 

 irregularities of surface ? If the former, we could not 

 imagine how the condition for determining continental areas 

 and oceanic basins could be initiated. We are therefore led 

 to accept the alternative hypotheses as more in accord with 

 known facts. But the root matter here contemplated involves 

 the conclusion that prior to the cooling and condensation of 

 the gaseous vapours, which eventually occupied the 

 primaeval ocean basins, the forces of themselves then at 

 work were equal to the task of producing irregularities on 

 the earth's surface, whether by contraction expansion, or 

 transfer, sufficiently grand in scale to form more or less 

 elevated continental areas in the midst of basins grand 

 enough to receive the oceanic waters. There may not have 

 been at this stage either deep abyssal regions on the one 

 hand nor high mountain peaks on the other, but it is almost 

 certain that forces then at work sufficed to produce such 

 relative elevation and depression, as are now supposed by 

 many to be only rendered possible by changes in the loaded 

 surface caused by the transfer of superficial solid matter 

 mainly through aqueous agencies. A diversified distribution 

 of the surface magma is assumed with good reason by 

 Mallet, J. D. Dana, Prof. Hennessy, Archdeacon Pratt, 

 Geikie, and many other eminent physicists and geologists, 

 as a primary condition ; and this primary condition, owing 

 to the unequal rates of cooling, and differences of density of 

 different masses of magma, is assumed to be the initial 

 factor in producing elevated and depressed surfaces. Dana 

 in his last work ("Manual of Geology," 3rd edition, 1879) 

 states : — " The fact that the continental and oceanic areas 

 were determined in the first cooling of the globe signifies that 



