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



showing no trace of the original subterranean movements to which 

 those contortions are due. 



In straining our eyes through the darkness of past time to ima- 

 gine, as best we can, the methods of operation through which nature 

 has attained the results which we now see, compulsion is laid upon 

 us to entertain many new and strange conceptions of the things 

 which have been done by Time and Porce. Gradually, however, we 

 become accustomed to a new order of ideas ; and no theory need 

 really startle us which complies with these two conditions : — first, 

 that it shall ascribe to known causes nothing but known effects ; and, 

 secondly, that the combination of causes which it assumes shall be 

 required for the explanation of facts which are thoroughly esta- 

 blished and ascertained. But having more than enough to do to 

 explain those facts of nature which are of this undoubted character, 

 it is indeed a waste of ingenuity when we construct elaborate theories 

 to account for facts which either do not exist at all, or exist only in 

 a very different connexion from that in which we have by assump- 

 tion placed them. The facts assumed by the theory are in my opi- 

 nion to a large extent as purely hypothetical as the ingenious expla- 

 nations which are invented to account for them. In support of this 

 opinion I shall have to adduce in some detail independent evidence 

 derived from that portion of the Highlands with which I am best 

 acquainted. But in the meantime I may point out admissions in- 

 volved in our author's own words, which seem to me to carry us a 

 long way towards conclusions opposed to his. 



We have seen that, when describing the foldings of the Highland 

 strata, he compared them to those waves of the sea which are driven by 

 a fresh gale from the north-west, and that he pointed to the map of 

 the country as indicating by its leading lines the respective directions 

 in which the longer and shorter axes of these waves have run. This 

 of itself is a strange admission to be made by an author who proceeds 

 to assure us in a later page that, " if subterranean movements ever made 

 any show at all upon the surface, they have been effaced long ago" (!). 

 But the fact thus admitted is too remarkable and significant to be 

 passed over merely as illustrating the general truth of a poetical com- 

 parison. Look at the map of the north-west coast of Scotland. Nothing 

 can be more striking than the general prevalence of hues having a 

 l^.'E. and S.W. direction. It is not merely the great vaUey of the Cale- 

 donian canal with its chain of lakes running, as that valley does, 

 across the whole breadth of the island, but it is also the general 

 direction, with only an average deviation, of many of the great sea- 

 lochs and of some of the great freshwater lakes of the Highlands. 

 Ko geologist, even one who had never seen the country, could look 

 on that map without being certain at a glance that there must be a 

 geological cause for such a general prevalence of direction, and that 

 the lines of physical geography were also in some way hues deter- 

 mined by lines of geological structure. Accordingly Mr. Geikie is 

 himself compelled to admit that with reference to these "longitudinal" 

 valleys, the agencies of erosion have been guided in their work by 

 the prevailing strike of the strata, w^hich strike, as he also admits, is 



