258 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 5, 



began, it is in the highest degree improbable that they all re- 

 mained under water by the time it ended. Even, therefore, in 

 the case supposed, it is probable that the same movement which 

 rolled and crumpled the strata, elevated at the same time into dry 

 land great portions of the bed of the sea. The form, again, in 

 which that sea-bed rose above the waves would be determined by 

 the lines of subterranean elevation, and along those lines the new 

 agencies of atmospheric denudation would be compelled to act. The 

 theorist, therefore, who maintains that movements of such tremendous 

 power as those which are admitted to have tossed the strata of the 

 Highland mountains, have nevertheless had but a subordinate part 

 in determining the existing physical geography of the country, can 

 have only one other hypothesis to suggest. He must suppose that 

 the strata of the Highlands, after all the tossing and crumpling, and 

 the movements affecting them were ended, still remained, or were 

 subsequently again submerged under the sea, and that thousands of 

 feet of new beds were laid down unconformably upon them, filhng 

 in all their folds, and covering up all their crests. He must further 

 suppose that these more recent deposits were again raised by some 

 new movement coming from a different quarter, and along different 

 lines of elevation. Then, indeed, these new lines of elevation wonld 

 be also the new lines of drainage, and the heights and hollows of the 

 new country might have little or no reference to the old " tossings " 

 which lay buried underneath. 



This accordingly is the theory which Mr. Geikie adopts in some 

 passages of his work, although it is wholly inconsistent with facts 

 which in other passages he himself admits. He states broadly that 

 little or nothing of the surface which we now see is due to the 

 squeezing, crumpling, and breaking to which the strata have been 

 subjected. He says : — " These changes went on beneath the surface 

 under a vast thickness of rock which has since been worn away. 

 There is now no trace of the original effects produced by these un- 

 derground movements upon the exterior of the earth's * crust.' If 

 they ever made any show there at all (which seems to me by no 

 means certain), they have been effaced long ago." 



To estimate the boldness of this assertion we have only to follow 

 the hypotheses it involves, and then to compare these hypotheses 

 with admitted facts relative to the structure of the country. Let it 

 be conceded that the contorted strata which now constitute the 

 mountains of Argyllshire were once covered by a great superincum- 

 bent mass of Old Red Sandstone. Let it be conceded also that this 

 superincumbent mass was wholly unconformable to the convoluted 

 rocks beneath, and that when raised into dry land it presented a 

 surface whose outlines had no reference to the old folded schists. 

 In this case it is of course quite possible to suppose that lines of de- 

 pression in this Old-Eed-Sandstone country might correspond with 

 lines of elevation in the more ancient rocks below, or might cut 

 across them at every variety of angle and inclination. Now let 

 us trace out what must have happened in some such instance. Let 

 us suppose the Old-Eed-Sandstone depression running along a line 



