UPPER SILURIAN. 237 



Water-lime is so called because used for making water- (or hydraulic) 

 cement ; it is a drab-colored or bluish impure limestone, in thin layers. 

 At Bernardston, Mass., a few miles west of the Connecticut (on the 

 land of Mr. "Williams), there is a Crinoidal limestone, which, as C. 

 H. Hitchcock has stated, is either Lower or Upper Helderberg. It 

 underlies quartzyte and mica slate. The same formation, though 

 without limestone, extends, as the author has ascertained, northeastward 

 to South Vernon, where it includes staurolitic slate, hornblende rocks, 

 gneiss, and mica slate ; and these rocks are the kinds characteristic of 

 the Coos group of Hitchcock, which stretches northward through 

 New Hampshire, east of the Connecticut, and probably also south- 

 ward through Massachusetts and Connecticut, to the region west of 

 New Haven. 1 Rocks of this era extend from northern New Hamp- 

 shire over Maine, to New Brunswick and Nova Scotia. 



The following are the several New York subdivisions, beginning below, — 1. Ten- 

 taculite and Water-lime group, 150 feet in the Helderberg Mountains. 2. Pentamerus 

 limestone, 50 feet in the Helderberg Mountains. 3. Catskill or Delthyris Shaly lime- 

 stone. 4. Encrinal limestone. 5. Upper Pentamerus limestone. 



An analysis of the Water-lime rock afforded Dr. Beck — Carbonate of lime 48-4, 

 carbonate of magnesia 34 3, silica and alumina 13-85, sesquioxyd of iron 1*75, moisture 

 and loss 1-70. One of the beds of the Water-lime strata, consisting of thin clinking 

 layers, abounds in fossils called Tentaculites, and has been named Tentaculite limestone. 



The Pentamerus limestone (No. 2), overlying the Water-lime, is so called from its 

 characteristic fossil, Pentamerus galeatus (Fig. 462). It is compact, and mostly in 

 thick layers. The Catskill or Delthyris Shaly limestone (No. 3) consists of shale and 

 impure thin-bedded limestone, and, in many places in New York, abounds in the large 

 fossil shell Spirifer macropleura Con. It extends as far west as Madison County, 

 and is full of fossils. The Encrinal limestone (No. 4) is confined to the eastern part of 

 the State. The Upper Pentamerus (No. 5), the upper layer, is of limited extent, but 

 has many peculiar fossils: it is named from the Pentamerus pseudo-galeatus H. (Figs. 

 464, 485). 



The Saliferous beds pass rather gradually into the Water-lime, — their upper layers 

 becoming more and more calcareous, and containing some of the Water-lime fossils. 



In Ohio, the rocks outcrop (owing to the extension northward of the Cincinnati up- 

 lift, p. 217) over a north-and-south region extending from the western portion of Lake 

 Erie southward (Newberry), nearly to the Ohio river, and westward into Indiana. The 

 rocks make part of the "Cliff limestone " of the Interior basin (so called because it 

 stands in cliffs along the river valleys). 



In West Tennessee, light-blue limestones of this period, abounding in fossils, occur in 

 Hardin, Henry, Benton, Decatur, and Stewart counties. The maximum thickness is 

 about 100 feet. In southern Illinois, there are beds of siliceous limestone underlying 

 the Clear Creek limestone, the lower part of which Worthen refers to this period; they 

 rest directly upon limestones of the Cincinnati or Hudson River age (the Cape Girard- 

 eau limestone of the Missouri Report), no Niagara limestone intervening (Worthen). 



In the Appalachian region in Pennsylvania, the Water-lime group has, in the middle 

 belt of the mountains, a thickness in some places of 350 feet, while in the southeast 

 belt it is 50 to 200 feet : it thickens to the southwestward. The rest of the Lower 

 Helderberg, consisting also of impure limestones, has a thickness of 100 feet or more 

 in the middle belt, and 200 to 250 in the southeastern, which thickness is maintained 

 along the Appalachian chain. (Rogers.) The beds have not been observed in East 

 Tennessee. 



1 Amer. Jour. Sci., III. vi. 1873. 



