194 Sir A. Qcikic — Lamarck and Playfair — 



on wluoh the surface of the land undergoes disintegration, he could 

 see no difficulty in conceiving that the mere passage of running 

 water over that surface must inevitably lead to tlie erosion of 

 a system of drainago-lines from the mountain-crests down to the 

 margin of the sea. In language closely similar to that employed 

 at the same time by Playfair in the volume which appeared at 

 Edinburgh, ho remarks : — " If Ave suppose the exposed part of the 

 surface of the earth to have been originall}' a vast plain, unvaried 

 either by mountains or valleys, and having no other curvature than 

 that of the general form of the globe, though such a supposition is 

 not necessary, seeing that the lands successivel}' abandoned by the 

 ocean in its westerly movement would not all be without irregularities 

 in their surface, I can easily show that at the end of a certain period 

 of time the influence of the subaerial waters will have modified or 

 destroyed the regularity of surface of tliis plain, and will ultimately 

 form mountains like those which are familiar to us " (pp. 11, 12), 

 " This sequence of events is that followed by Natiire in her known 

 methods and processes which can be seen in progress everj' day 

 before our eyes. It is thus evident to me that every mountain which 

 is not the result of A"olcanic eruption or of some other local 

 catastrophe has been cut out of a plain, and that its peaks and crests 

 mark the relics of the ancient level of that plain " (p. 14). 



That this interpretation holds true for the abundant hills and 

 mountains composed of horizontal or little disturbed stratified 

 formations is now an accepted conclusion of modern geology. But 

 it will not explain the origin of the great mountain-chains of the 

 earth's surface, which have been upheaved during the violent 

 plication and rupture of the terrestrial crust. Of the real structure 

 of such chains comparatively little was known in Lamarck's time, 

 and even that little was not appreciated by him. He thought that 

 the inclined arrangement of strata in many mountains was original, 

 and might generally be taken to indicate the position of the shores 

 on which the sediments were deposited, though it might in some 

 cases be due to local disturbance. lie knew that sometimes the 

 strata in a mountain-chain are found to be vertical, but he would 

 not on that account invoke for their explanation some universal 

 catastrophe as had been advocated by other writers,' but contented 

 himself with a vague reference to local subsidences (pp. 22, 23). 



In his account of what he conceived to take place when the land 

 is laid bare in consequence of the westward migration of the ocean, 

 Lamarck involved himself in some curious contradictions. In the 

 mental picture which he drew of the successive emergence of the 

 marine deposits, including the granite ridges which had been laid 

 down xipon the sea-floor, he imagined that the surface of the plain, 

 thus transformed into an area of land, was gradual!}' heightened by 

 the accumulation upon it of the remains of organisms, more especially 



^ Ho uot improlmblv had Cuvier iu his miud, who lield this opinion and afterwards 

 pave it inoniinouoo iu Ins " Discours sur les E^vohitions de hi Surface du Globe," 

 whciviu ho assorted that tho occurronco of such a catastrophe, some 6,000 yetirs ago, 

 was one of the best ascertained facts in geology. 



