PALEOZOIC TIME — DEVONIAN. 693 



at Rock Island, etc.; Wisconsin, north of Milwaukee; in Iowa, near 

 Independence; on the Mississippi, shale (Marcellus) overlaid by limestone ; 

 and in Missouri. The greatest thickness is along the Appalachian region, 

 where the beds are almost wholly f ragmental ; and within these limits in 

 Monroe County, eastern Pennsylvania, the group is 2000 to 5000 feet thick. 



The Hamilton group of New York has as its lower member, the Marcellus 

 shale, a formation of soft, black shale, except near the bottom, where occurs 

 a thin limestone stratum called the Goniatite limestone. The shale is 

 bituminous, and much unavailing search for coal has hence been made in it. 

 Hall states that in many places it contains so much bitumen as to give out 

 flame when thrown into a fire of hot coals. Its fossils are few in species, 

 and mostly small, excepting the Goniatites. 



Above the Marcellus come the true Hamilton beds — chiefly shaly sand- 

 stones with some fine shales and thin limestone layers ; and at top, in many 

 places, the Tully limestone, 10 to 20 feet thick,which is, by some, made the base 

 of the Upper Devonian. This limestone is sometimes referred to as the 

 Cuboides zone, in reference to a common fossil, Rliynchonella cuboides. 



In eastern New York, in Ulster, Green and Albany counties, the Hamilton 

 affords "the North River flagstone," affording excellent flags and pavements, 

 used much in New York and the adjoining states. The thicker layers are 

 called bluestone, from the bluish gray color. The bluestone is easily worked 

 by machine-planing for use in the trimmings of buildings, and is convenient 

 for the purpose if the stone can be selected that will not drip iron stains down 

 the front below a course of it. The flagstone contains an occasional, slender 

 worm-boring, and coaly fragments, and is often ripple-marked, like other 

 layers of the Hamilton. Moreover, the strata are frequently intersected by 

 joints of great extent and regularity. The scene in Fig. 121, page 112, is 

 from the Hamilton near Cayuga Lake. 



In eastern Canada, at Gaspe and Baie des Chaleurs, a middle portion of 

 the 7036 feet of Devonian sandstones is referred to the Hamilton or Middle 

 Devonian ; and the next above to the Upper Devonian. The Little River 

 group of Nova Scotia, and Cordaites shales and flags of St. John County, 

 New Brunswick, are referred to the Hamilton by Dawson. 



West of the Mississippi, in the Eureka district, Nevada, the 8000 feet of 

 Devonian limestone and shale include the Hamilton group; but it has not 

 heen found possible to separate the Hamilton portion. Hamilton beds are 

 also found in the valley of the Mackenzie River, between Clear Water River 

 and the Arctic Ocean, some of the species of fossils being identical with 

 those of the United States and Canada (Meek). 



Interior Continental Begion. — The Hamilton beds of New York are separated 

 into two parts by a thin layer of Encrinal limestone. The annexed section (by Hall) is 

 from the borders of Lake Erie. The Hamilton beds, 10 b, include (1) blue shale, (2) En- 

 crinal limestone, (3) Upper or Moscow shale ; the Tully limestone is wanting. Above lie 

 (10 c) the Genesee slate, and (11) a following part of the Portage group, both of the Upper 

 T)evonian. A section near Canandaigua Lake, in Ontario County, N.Y., includes, accord- 

 dana's manual — 38 



