on American Geology, 89 



west by (2nd.) the Ococee conglomerates and sandstones, with 

 argillites, chloritic, talcose and micaceous slates, and occasional 

 bands of limestone, all dipping, like the rocks of the 1st division, 

 to the S. E. In the 3rd place we have the Chilhowee sandstones 

 and shales, several thousand feet in thickness, including near the 

 summit beds of sandstone with ScoUthus, and considered by Mr. 

 Safford the equivalent of the Potsdam. (4th.) The Magnesian 

 limestone and shale group, also several thousand feet thick, 

 and divided into three parts ; first, a series of fucoidal sandstones 

 approaching to slates and including bands of magnesian limestone ; 

 second, a group of many hundred feet of soft brownish, greenish, 

 and buff shales, with beds of blue oolitic limestone, which as well 

 as the shales, contain trilobites. Passing upward these lime- 

 stones become interstratified with the third sub-division, consisting 

 of heavy bedded magnesian limestone,more or less sparry and cherty 

 near the summit. The limestones of Knoxville belong to this group, 

 which with the 3rd or Chilhowee group is designated by Mr. Saf- 

 ford as Cambrian, corresponding to the Primal and Auroral of 

 Rogers, or to the Potsdam and Calciferous sandrock, with the pos- 

 sible addition of the Chazy, being equivalent to the great Magne- 

 sian limestone series of Prof. Swallow in Missouri. To these 

 strata succeed Safford's 5th formation, consisting of limestones, the 

 equivalents of the Black River, Trenton and higher portions of 

 the Lower Silurian. 



In Eastern Canada we find a group of strata similar to those 

 described by Rogers and Safford, and distinguished by Sir Wil- 

 liam Logan as the Quebec group. It has for its base a series of 

 black and blue shales, often yielding roofing slates, succeeded by 

 grey sandstone and great beds of conglomerate, with dolomites 

 and pure limestones, often concretionary and having the character 

 of travertines. These are associated with beds of fossiliferous 

 limestones, and with slates containing compound graptolites, and 

 are followed by a great thickness of red and green shales, often 

 magnesian, and overlaid by 2000 feet of green and red sandstone, 

 known as the Sillery sandstone, the whole from the base of the 

 conglomerate, having a thickness about 7000 feet. These red 

 and green shales resemble closely those at the top of the Hudson 

 River group, and the succeeding sandstones are so much like those 

 of the Oneida and Medina formations, that the Quebec group was 

 for a long time regarded as belonging to the summit of the Lower 

 Silurian series, the more so as by a great break and upthrow to 



