Lesley.] 106 [November. 



tions : No. X, white sandstone, 2000 feet, No. IX, red sandstone, 

 5000 feet. No. VIII, green and olive shale, 8000 feet; the white 

 sandstone including rarely a thin bed of conglomerate here and there, 

 and traces of coal-plants and even thin coal-beds; the red sandstone 

 passing downwards into red shale, and often alternating flinty sand- 

 rock with massive mud-rocks even in the upper part; and the olive 

 shale becoming near the base of it rocky, and even mountainous in 

 the region of the Juniata, where a system of thin coal-beds was also 

 developed in the midst of the sandstone and shale. The white sand- 

 stone of No. X becomes in the Alleghany Mountain belt less than 

 800 feet thick, and is there characterized by thin-bedded and very 

 irregularly cross-bedded sandstones of a peculiar greenish tint and 

 harsh, rough fracture, weathering to a surface sprinkled with small 

 red dots of peroxide of iron. 



It is not too much to say that a geologist well accustomed to these 

 formations, along their great Appalachian belts of mountain and 

 valley, stretching from the Appalaehicola and Alabama Rivers in the 

 South, to the Delaware and Hudson in the North, cannot fail to re- 

 cognize them and distinguish them anywhere. The tout ensemble or 

 fades of each is sui generis. Fossils may come in afterwards as a 

 satisfactory confirmation ; but the eye has already determined the 

 respective formations. Even in the West, where Formation IX has 

 dwindled, like Formation XI, to an insignificant one or two hundred 

 feet, and scarcely separates the green sands of X from the green shales 

 of YIII, the characteristic features of the three formations, although 

 modified and harmonized by the preponderance of the argillaceous 

 element, are still in sufficient contrast to be recognized when fairly 

 seen. 



To an eye thus trained among the broad outcrops of the Lower, 

 Middle, and Upper Devonian of the Appalachians, it is evident that 

 the mountains of Cape Breton and the hills of Northern Nova Scotia, 

 surrounding or intervening between the already-mentioned red shale 

 borders of the coal areas, are composed of these formations. True, 

 the anticipation of finding these formations has a tendency to warp 

 the judgment and delude the eye, especially when that anticipation 

 is based upon such a probability as this : that a iiiassif, three miles 

 thick and a thousand miles long, will maintain its thickness (and of 

 course its topographical height and geographical breadth) at least as 

 far along the prolongation of its isometric axis (to use Mr. Hull's 

 new and much-needed term), as will such minor formations as the 

 Coal over it or the Upper Silurian limestones under it. In other 



