186 Geological Gleanings. 



" We cannot expect that the Coal formation, with its land-de- 

 rived materials and its abundant land plants — far more abundant 

 in the east than in the west — will prove an exception to this gene- 

 ral rule ; and when we find that these strata have a thickness of 

 mor- than fourteen thousand feet in Nova Scotia, according to 

 the measurements of Sir W. E. Logan ; that the productive coal 

 measures in Cape Breton are estimated by Mr. Brown to exceed 

 ten thousand feet ; and that in Pennsylvania, the coal measures, 

 including the conglomerate, may be about eight thousand feet, 

 and in the Mississippi valley one thousand feet, — we are forced to 

 the conclusion already suggested of the ultimate disappearance 

 of the coal measures in that direction. 



' l It would therefore appear, that from the earliest Silurian 

 times, the Great West, or the region of the Ptocky Mountains, has 

 been an ocean, which successively received the finer sediments 

 derived from eastern lands, or which produced within its own area 

 the calcareous deposits, but ever, an ocean, not only to the close 

 of the Carboniferous period, but still later through the Permian, 

 Jurassic and Cretaceous periods ; showing apparently no evidences 

 of dry land till about the beginning of the Cretaceous era, or per- 

 haps a little earlier ; while in later Tertiary periods, the conti- 

 nental fauna and flora have been remarkably developed over the 

 same area. 



"Thus while the older Palaeozoic formations have been largely 

 accumulated in the east, in successive beds, having altogether a 

 thickness of several times the height of our highest mountains, 

 they have greatly diminished in the west. At the same time, 

 while the. Post-pa!?eozoic formations are very thin or often absent 

 in the east, they have accumulated in vast amount along the line 

 of the Rocky Mountains, from one end of the continent to the 

 other." 



These are hints of great general truths, of profound significance 

 in geology : but a much larger induction of facts than we at pre- 

 sent possess, is required to give them certainty ; and they 

 will be found to be liable to many local exceptions, even if fully 

 established for the continent at large, 



Canadian Geology. — Prof. Chapman introduces to us two new 

 species of the genus Asajihus, found in the lower Siluriai rocks 

 of Upper Canada, and which he names A. Canadensis and A. 

 Halli. (Canadian Journal, May.) 



We are also indebted to Prof. Chapman for a very valuable 



