APPENDIX. 439 



Note IV., page 132. 



The term Catskill group is employed in this connection in a sense great- 

 ly restricted from that in which the New York geologists originally em- 

 ployed it, since it has been shown that the principal portion of the so-call- 

 ed Catskill strata of the Catskill Mountains is really a prolongation of the 

 Chemung rocks of the southern interior of the state ; and for this reason, 

 the original sense of the term is no longer admissible. The term thus 

 stands as the designation of a series of strata which does not form a nat- 

 urally restricted assemblage, and must drop out of use. 



In parallelizing the "Catskill" (thus restricted) and the "Marshall" with 

 the lower part of the Mountain Limestone of Europe, and at the same time 

 suggesting their synchronism with the "Old Red Sandstone," I employ the 

 latter term in its restricted and original sense, not as comprehending the 

 whole recognized Devonian of the Old World. It is farther not unlikely 

 that the parallelism ought to be restricted to the "Yellow," "White," 

 and " Red" sandstones and conglomerates (Marwood and Petherwin beds) 

 of the Old Red series, which, according to admissions made from time to 

 time by Murchison and others, exhibit almost decisive affinities with the 

 Carboniferous age. See Quar. Jour. Geol. Soc, London, vol. ix., p. 23. 



Note V., page 139. 



Allusion is here made to one of the mines at Lasalle, Illinois. This by 

 no means exemplifies the greatest depth to which mining operations have 

 been cai-ried. The mine at Duckenfeld, in Cheshire, England, is probably 

 the deepest coal mine in the world. A simple shaft was sunk 2004 feet 

 to the bed of coal, and by means of an engine plane in the coal-bed, a far- 

 ther depth Of 500 feet has been attained, making 2504 feet to the bottom 

 of the excavation. At Pendleton, near Manchester, coal is worked daily 

 from a depth of 2135 feet ; and the Cannel coal of Wigan is brought from 

 1773 feet below the surface. Many of the Durham collieries are equally 

 deep, and far more extensive in their subterranean labyrinths. 



The engine shaft of the Great Consolidated copper mines in Cornwall 

 reaches the depth of 1650 feet, and the length of the various shafts, adits, 

 and galleries exceeds 63 miles. Dalcoath tin mine, in Cornwall, is now 

 working at more than 1800 feet from the surface. The famous silver 

 mine of Valenciana, Mexico, is 1860 feet deep. The Hohenbirger mines 

 in the Saxon Erzegebirge, near Ereiburg, are 1827 feet deep, and the 

 Thurmhofer 1 944 feet deep. The depth of the celebrated mine of Joa- 

 chimsthal, in Bohemia, is 21 20 feet. The Tresavean copper mine in Corn- 

 wall is 2180 feet. The workings of the Samson mine at Andreasberg, in 

 the Harz, have been prosecuted to the depth of 2197 feet. At Rorerbuhel, in 

 Bohemia, there were in the 16th century excavations to the depth of 3107 



