1802.] BIGSBY C.U1BBIAX AXD HUKOXIAN. 39 



These conglomerates and sandstones, sometimes 1500-3000 feet 

 thick, are local ; and they are called Cambrian because they occupy 

 the place of that formation in the geological series ; but they have 

 no affinity with the Cambrian of Wales, for, both in Europe and 

 America, they are merely the re-cemented fragments of the crystalline 

 rock on which they repose. The same is to be said of the bed near 

 Kinnekulle, in Sweden, which lies between the granitic gneiss there 

 and the Silurian strata ; it consists in like manner of re-adhering 

 fragments of the metamorphic rock below — the " arkose " of Bron- 

 gniart. These are important facts, and they derogate not a little 

 from the high rank at present held by the Cambrian as a system. 



The schistose form of Cambrian and the local puddingstone variety 

 do not form constant and widely diffused strata, like those of many 

 kinds of rocks in the palaeozoic and mesozoic series, the conglomerate 

 being native, the other comparatively foreign. 



According to our present information, the direct superposition of 

 Silurian upon metamorphic rocks, mentioned in § 3, prevails over 

 considerably more space than the schistose or conglomeratic inter- 

 mediates. We find them in close adhesion for 2000 miles, from 

 Labrador westward to Minnesota beyond the Mississippi River. At a 

 multitude of points along this line they have been examined by 

 Logan, Murray, Chapman, Richardson*, myself, and others, — on the 

 shores of Labrador, Lake St. John (L. Canada), near Quebec, 

 Montreal, Kingston, Lake Simcoe, on the Great Lakes, and so on. 



Professor Haughton, in the Appendix to M'Clintock's ' Fate of 

 Sir John Franklin,' broadly states that " the Silurian rocks of" the 

 Arctic Archipelago rest everywhere directly on the granitoid rocks, 

 with a remarkable red sandstone, &c. ;" and, I suppose, transgres- 

 sively, seeing that the Professor finds the Upper Silurian beds there to 

 be horizontal. The same immediate contact takes place in the 

 Appalachians and on the Upper Mississippi f. 



In the excellent account of the geology of Bolivia and Southern 

 Peru, by David Forbes, Esq., F. It. S.J, the word " Cambrian " never 

 occurs. Silurian beds of enormous thickness, with Cruziana Boli- 

 viano, and Annelid-tracks, are said to rest directly on granite. Nor 

 does the Cambrian show itself in either of Mr. Forbes's two sections 

 (335 and 328 miles long respectively) through these countries, 

 abounding in palaeozoic strata. In the neighbouring province of Chi- 

 quitos M. d'Orbigny observed the same facts ; and also on the flanks 

 of the lofty Illimani, a part of these Cordilleras §. 



This direct contact obtains also in Scandinavia, as at Andrarum, 

 &c, in Scania, and in the Silurian trough of Christiania, Norway |j. 

 As regards Bohemia, M. Barrande expresses himself very satisfac- 

 torily on this point in * Bulletin Soc. Geol. de France,' n. s. vol. x. 



* Logan and Murray, Geol. Reports, passim ; Chapman, Canadian Naturalist ; 

 Richardson, Geol. Reports, Canada, 1857, p. 78. 



t Rogers and D. D. Owen, Reports on Pennsylvania and Minnesota. 



| Quart. Journ. Geol. Soc. vol. xvii. 



§ Travels in South America, vol. iii. pp. 146, 225. 



II Sir R. I. Murchison, Quart. Journ. Geol. Soc. vol. xi. p. 162. 



