322 ILLOGICAL GEOLOGY. 



strata ; but in the Rhenish provinces, certain &quot; qnartzose 

 flagstones and grits, like tliosc of the Longmyml,&quot; are 

 seemingly concluded to be of contemporaneous origin, be 

 cause of their likeness. &quot; Quartzites in roofing-slates with 

 a greenish tinge that reminded us of the lower slates of 

 Cumberland and Westmoreland,&quot; arc evidently suspected 

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

 boniferous limestones &quot; 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 ; &quot; and in calling this group, as he does, 

 the &quot; representative of the millstone grit,&quot; Sir R. Murchi- 

 son clearly shows that he thinks likeness of mineral compo 

 sition sonic evidence of equivalence in time, even at that 

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

 the United States, such similarities arc looked for, and con 

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

 chison contends theoretically for this relation between litho- 

 logieal character and date. For on the page from which 

 we have just quoted (Siluria, p. 38V), he says, that &quot;whilst 

 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 Valdai 

 Hills arc represented on the western llank of that chain, by 

 hard, contorted, and fractured limestones.&quot; Uut these, 

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

 himself asserting that the Potsdam-sandstone of North 

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

 of Scandinavia arc 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. In 

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

 uer continues to influence geological speculation ? 



