GEOLOGICAL MUTATIONS. 27 



preserved so as to prove that they ever existed. It is only so long as the coral is fresh that 

 it is hard and impenetrable ; when raised above or below the proper depth which suits the par- 

 ticular species, the coral polype dies, and if exposed to the air the coral rots, and if then exposed 

 to the wash of the sea is swept away. He himself narrates his experience of the rotting of the 

 coral, but on the other hand he also speaks of having heard of two coral islands which had 

 been elevated thirty or forty feet above the sea and showed a face of perpendicular coral cliffs to 

 the sea : these, however, had not been examined by any naturaKst.* 



If I am not mistaken, objections have been taken by some authors to the hjqjothesis of a sub- 

 merged continent, on the ground that it might disturb the equiHbriimi of the earth. There is no 

 doubt that on this point the arrangements, instead of being of a compensatory nature, are directly 

 the reverse. A mass of material like the mountain-ranges protruded to one side further from the 

 fidcrum (the centre of the earth) than the rest of its crust, must have a tendency to make the earth 

 lop-sided, and a depression on the opjjosite side diawiug the weight nearer to the fulcrum, and 

 thereby diminishing its force, instead of being a compensatory movement, would only add to the 

 disturbance. It is for astronomers and physicists to determine whether there is anything iu the 

 objection. I may, however, remark, that the parts where there is the greatest subsidence may not 

 be opposed to those where there is the greatest rise : . that subsidence and elevation often take place 

 side by side, and that the whole alteration on the equilibrium even at the greatest, is probably 

 too trifling to have any effect on such a large body as the earth. 



As to the date when this continent or these continents existed, and when they became submerged, 

 we have more than one indication which may assist us in. coming to a conclusion. In the first 

 place, it is a generally acknowledged principle that important geological revolutions are slow and 

 deliberate, and extend over a long pciiod of time ; that the crust of the earth is not perpetually 

 bobbing up and dowoi ; and that the oscillations which occur in every part of the globe are mere 

 minor accidents, as it were incidental to the progress of the great movement, and not the great 

 movement itself. They may be compared to the slightly tremulous movement of a man's hand when 

 he heaves his food to head : the real movement is the raising of his hand ; its vibration is the 

 incidental. 



One phase of these geological mutations is the alternation of bands of elevation and depression. 

 It was, I think, Mr. Darwin who suggested this idea, and at any rate it was was his discoveries 

 relating to the jihysical and geological history of coral reefs, which brought it into favour. It is 

 matter of fact that the elevation and corresponding depression iu the two bands generally lie along- 

 side of each other. The Andes of South America is a band of elevation; to the west of that range 

 there is a depression of immense depth, almost without islands or reefs ; westward of that gulf 

 there is a vast area of coral atolls and reefs, which, as a whole, have been, and perhaps still are, 

 sinking, while through it extends a band of rising land, distinguished by numerous volcanoes. The 

 North Atlantic is a band of depression, Europe a recent band of elevation. "Where active vol- 

 canoes are in operation, the land is visually rising ; and these generally lie in bands which 

 often end in reaching to the dignity of mountain chains. Such is the band which extends from 

 the New Hebrides through New Guinea, Borneo, Java and Sumatra. It seems ' a necessary con- 

 sequence of the elevation of diy land in the northern hemisphere, that a corresponding de- 

 pression should have taken place somewhere else. The elevation of, at least, all the land which 



* Dakwin's •' Coral Formations." 



