244 Outlines of Geology. 



and coaly matter, on the road between Edinburgh and Leith ; and 

 Mr. Greenough even informs us, that he found the same waving 

 lines in sandstone, now forming at Port Dinnleyn in Carnarvon- 

 shire. 



These curves are not less varied in their forms, than in their 

 dimensions ; they are sometimes only a few inches in extent, and 

 the whole may be included in a hand-specimen ; at other times 

 they extend many feet and yards, and even sometimes for many 

 miles. Saussure, in his Travels in the Alps, speaking of the shape 

 of these contortions, compares them to the letters Z and X, ex- 

 hibiting their angular and zigzag forms ; to the letter C, shewing 

 their tendency to circular flexure ; and on the road from Chamouny 

 to Geneva, a perpendicular surface of limestone exhibits the strata 

 in one part bent into arches, and producing, by their association 

 with the bendings in another part, a form not unlike the letter S. 



These curvatures are regarded by Dr. Hutton and Mr. Playfair, 

 to have originated in the elevation of the strata once horizontal, 

 while in a flexible and ductile state, by a force acting upon them 

 from below upAvards : owing to gravity and the resistance of the 

 mass, this direction became oblique, and the lateral force caused 

 contortion ; but this view, although ingenious, -and often con- 

 sistently applicable to the appearances, is sometimes, and indeed 

 often, so at variance with them, that it cannot be plausibly enter- 

 tained as a general cause ; among the leading militant instances, 

 we may advert to the existence of curved upon horizontal strata. 

 Near Malvern, limestone, much contorted, rests upon strata quite 

 horizontal. Mr. Greenough adduces, as another similar instance, 

 the singular stratification of Mont Righi, in which highly-curved 

 limestone rests upon strata preserving perfect horizontality : how 

 happened it, then, that a force adequate to the flexion of one part 

 of the limestone, elevated more than 7000 feet above the sea, 

 should not have affected the inferior beds ? A case still more 

 opposed, and indeed, if admitted in the abstract, fatal, to Dr. Hut- 

 ton's theory, may be seen upon the west side of Loch Lomond, 

 where veins of contorted slate traverse strata which are not con- 

 torted, not even disturbed. But if the Huttonian geologists are 



