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 is proved 

 by its large fossil Crinoids to be Lower or Upper Helderberg, prob- 

 ably the former. It underlies quartzyte and garnetiferous mica schist. 

 The same formation, though without limestone, extends, as the author 

 has ascertained, northeastward to South Vernon, where it includes 

 staurolitic mica schist, hornblende rocks, quartzose, gneiss, and mica 

 schist ; and these rocks are the kinds characteristic of the Cobs group 

 of Hitchcock, which stretches northward through New Hampshire, 

 east of the Connecticut. Near Littleton a limestone of the Upper 

 Helderberg contains fossil corals and Brachiopods. Rocks of this era 

 extend from Northern New Hampshire 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 Delthvris 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, 465). 



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. 



