336 ON THE APPARENT DISLOCATIONS [Ch. XV. 



the contrary, indeed, many kinds of this schist are equally, 

 if not more refractory in the furnace : but supposing the 

 quartz -rock to be less susceptible of being softened, how does 

 it happen that in other parts of the same series of rocks, the 

 quartz-rock partakes of every degree of flexure and con- 

 tortion ; and even pure quartz, in the form of veins of various 

 size, is very commonly seen traversing not only clay-slate, but 

 also gneiss, mica-slate, and other primary schists ; and " fol- 

 lowing the sinuosities of these rocks, however intricate, 

 without any fracture or breach of continuity." Surely, then, 

 if quartz-rock can be bent and contorted, at such a tem- 

 perature as attends the metamorphosis of sedimentary de- 

 posits into crystalline slates, or as is required to render the 

 whole mass of these slates soft and ductile, it caunot be 

 admitted that the appearance under consideration is a proof 

 of fracture. But even if this objection be not allowed, 

 another immediately presents itself, which is indeed of an 

 analogous nature : what we have just seen to occur in the 

 layers of a single curve composed of different rocks, we find, 

 on the large scale, to extend over considerable tracts ; thus, 

 immense beds of contorted rocks alternate with those which 

 are comparatively straight and regular, and this holds good 

 whether the whole mass of strata is highly inclined or nearly 

 horizontal, that is, according to the prevailing opinion, 

 whether it has been broken through and tilted up at a con- 

 siderable angle, or has been undisturbed. The description 

 of an occurrence of this kind in the Pyrenees, by Duhamel, 

 as quoted by Greenough from the Journal des Mines, clearly 

 shows the different manner in which parallel strata have been 

 arranged : " Compact felspar, trap, and limestone there form 

 an immense mass, composed of a prodigious number of alter- 

 nate beds of no great thickness, and inclined to the horizon 

 at a high angle : some of them are plain and regular, while 

 others are twisted in a thousand different directions, without 

 disturbing the parallelism of the beds above or beneath." * 



* The First Principles of Geology, p. 62. 



