570 



PARALLELISM OF CHAINS OF DIFFERENT AGE. 



than thirty miles in length, parallel to the elevations of the Rowley, Lickey and Char- 

 wood Hills, and specially affecting the Silurian System, and yet at right angles to the 

 direction of many masses of that system elsewhere. 



With such conflicting evidences, are we not led to infer, that it is impracticable to 

 define the period of any given line of elevation merely by its direction ? I am most 

 unwilling to have the appearance of rejecting too hastily, and from phenomena which 

 extend over a small portion of the surface of the globe only, that part of the ingenious 

 theory of one of the most distinguished geologists of the present day 1 , which implies 

 that deposits of the same age have been elevated upon lines more or less parallel. En- 

 tirely to reject this proposition would be to assert, that volcanic matter had never 

 burst out on parallel lines of fissure during the same periods of eruption, which is 

 contrary to the experience of geologists and to many facts contained in this volume. 

 No one, indeed, can have observed the linear direction of volcanic outbursts along sea 

 coasts, and habitual vents of eruption 2 , without acknowledging, that in accordance 

 with modern analogies, ancient parallel fissures of eruption must often be found 

 affecting deposits of the same age. But to whatever extent and under whatever limi- 

 tations this branch of the theory of M. Elie de Beaumont may be received, the facts 

 related in the preceding pages compel me to dissent from that part of it, which 

 implies, that deposits of a different age have necessarily been thrown up in divergent 

 directions ; since it has been demonstrated, that accumulations of very different ages 

 have been elevated during several successive ages upon the very same parallel. Thus, 

 for example, the chief fractures and the major axis of the coal-field of Coal Brook Dale, 

 as well as the striking dislocations on its margin, which affect the New Red Sand- 

 stone as well as the coal measures, are all coincident with the great north-east and 

 south-west movement by which the adjacent rocks of the Silurian and the Cambrian 

 System have been elevated ; nay, more, the ends of the very ridges, cited as the types 

 of the Silurian System, are prolonged into the heart of this coal-field, and thus the 

 forces which elevated the former have given the same direction to the latter ; though 

 the Silurian strata were set on edge anterior to the deposition of the coal measures. 

 The same phenomena are repeated in the Dudley and Tortworth tracts, though on 

 another line of dislocation common to them both. 



It has also been shown, that upon the direct prolongation of the axis of the Breidden 

 Hills, trending from W.S.W. to E.N.E., eruptions of igneous matter have been renewed, 

 at intervals, upon the same line of fissure, from the period of the Silurian System till 

 after the formation of the lias, as proved by a line of fissure extending from the 

 borders of Montgomeryshire through Shropshire into Staffordshire ; while the very 

 same deposits, i. e. rocks of ages as widely removed from each other as the Caradoc 

 sandstone and the lias, on the line of the Rowley, Clent, and Lickey Hills, have been 



1 M. Elie de Beaumont. See also the views of M. Boue. 



2 See Scrope on Volcanoes. 



