322 ILLOGICAL GEOLOGY. 



strata ; but in the Rbenisb provinces, certain " quartzose 

 flagstones and grits, like those of the Longmynd," are 

 seemingly concluded to be of contemporaneous origin, be- 

 cause of their likeness. " Quartzites in roofing-slates with 

 a greenish tinge that reminded us of the lower slates of 

 Cumberland and Westmoreland," are evidently suspected 

 to be of the same age. In Russia, he remarks that the car- 

 boniferous limestones " are overlaid along the western edge 

 of the Ural chain by sandstones and grits, which occupy 

 much the same place in the general series as the millstone 

 grit of England ; " and in calling this group, as he does, 

 the " representative of the millstone grit," Sir K. Murchi- 

 son clearly shows that he thinks likeness of mineral compo- 

 sition some evidence of equivalence in time, even at that 

 great distance. Nay, on the flanks of the Andes and in 

 the United States, such similarities are looked for, and con- 

 sidered as significant of certain ages. Not that Sir R. Mur- 

 chison contends theoretically for this relation between litho- 

 logical character and date. For on the page from which 

 we have just quoted {Slluria, p. 387), he says, that "w^hilst 

 the soft Lower Silurian clays and sands of St. Petersburg 

 have their equivalents in the hard schists and quartz rocks 

 with gold veins in the heart of the Ural mountains, the 

 equally soft red and green Devonian marls of the Yaldai 

 Hills are represented on the western flank of that chain, by 

 hard, contorted, and fractured limestones." But these, 

 and other such admissions, seem to go for little. Whilst 

 himself asserting that the Potsdam-sandstone of North 

 America, the Lingula-flags of England, and the alum-slates 

 of Scandinavia are of the same period — while fully aware 

 that among the Silurian formations of Wales, there are 

 oolitic strata like those of secondary age ; yet is his reason ■ 

 ing more or less coloured by the assumption, that forma- 

 tions of like qualities probably belong to the same era. I^ 

 it not manifest, then, that the exploded hypothesis of Wer- 

 uer continues to influence geological speculation? 



