President of the Geological Society for 1850. 29 



may be less imposing to the imagination than a vast thick- 

 ness of conglomerate or sandstone, or the bodily presence as 

 it were of a mountain-chain with all its inclined and curved 

 strata ; but the denuded tracts speak a clear and emphatic 

 language to our reason, and like mountain masses of fossil 

 nummulites, or of corals and shells, or seams of coal based 

 on under-clays full of Stigmaria and surmounted by erect 

 fossil trees, demand countless ages for their origin, and 

 these ages supply the time in which continents and moun- 

 tain-chains may rise and sink, without sudden, instantaneous 

 or paroxysmal action. 



I have already alluded to the slow crystallization and con- 

 sequent contraction of granitic mixtures, and to the expan- 

 sion of solid rocks by heat, and to the melting of stony masses, 

 together with various metamorphic agencies, as the causes of 

 slow and gradual movement, both vertical and horizontal. 

 Formerly, when the stratified materials of the Alps presented 

 to the eye of every observer a confused heap of ruin, before 

 any general laws governing the lines of longitudinal frac- 

 ture, or the parallel foldings of the strata, were caught sight 

 of, it might be argued, that such chaotic disorder implied one 

 or more paroxysmal outbursts of subterranean force, wholly 

 different from ordinary volcanic or any other known agency. 

 But Sir Roderick Murchison agrees with an eminent foreign 

 member of this Society, Professor H. D. Rogers of the 

 United States, and with several Swiss geologists of distinc- 

 tion, that the dislocations and lateral movements of Alpine 

 strata have been obviously regulated by general movements, 

 in which system and law can be discovered. Mr Rogers, you 

 will remember, declared in this room, when describing the 

 structure of the Alps and Jura, that he recognized a striking 

 analogy between the form of the flexures discernible in these 

 European chains and those observed by him and his brother 

 in the Appalachians of North America. In both cases the 

 successive parallel folds have on one side a steep, short dip, 

 while the other side of the anticlinal flexure is longer and 

 less inclined. This longer side, in the Appalachians, or Al- 

 leghanies, dips towards the belt of intrusive volcanic rocks 

 on the south-east flank of the chain. So in the Alps, the 



