56 Prof. Sedgwick on the general Structure 



mined their line of bearing, had ceased to act before the completion of the 

 old red conglomerates. 



In the region above described there is no connexion between the direction 

 of the valleys and the mean line of bearing of the formations ; and one of the 

 means successfully used by M. Elie de Beaumont in grouping together distant 

 mountain chains^ would, in this instance, entirely fail us. I do, however, think 

 that the leading doctrine of the Essay on the Epochs of Elevation (viz., that 

 mountain chains elevated at the same period of time have, even when widely 

 separated from each other, a general parallelism in the bearing of their com- 

 ponent strata), receives a strong confirmation from the position of the older 

 formations of the British Isles. 



It is now generally allowed that the old chains of mountains, mainly com- 

 posed of clay-slate and greywacke, which give so great an impress to the 

 physical character of this island (viz., the chains of Cornwall, of North Wales, 

 of the Isles of Man and Anglesea, of Cumberland, of Lannermuir, including 

 the whole range from St. Abb's Head to the Mull of Galloway, &c. &c.), are 

 nearly of the same age, and were probably all elevated before or during the 

 period of the old red sandstone. Now if a line be drawn along the axis of 

 the Cornish chain ; a second parallel to the prevailing ranges of the higher 

 Welsh mountains, as laid down in Mr. Greenough's map; a third in the direc- 

 tion of the strata of Anglesea; a fourth in the axis of the greywacke chain of 

 the Isle of Man ; and a fifth from St. Abb's Head to the Mull of Galloway ; 

 all these lines will make a near approach to parallelism with the line of bearing 

 in the system of the Cumbrian mountains, as established by the previous details. 

 Is this parallelism accidental ? I am unwilling to believe it ; and although 

 there are even in England some remarkable exceptions to this arrangement, 

 I think that the facts here stated afford, as far as they go, a confirmation of 

 that principle on which are founded many of the bold generalizations of the 

 extraordinary essay of M. Elie de Beaumont, to which I have alluded. 



§ 3. On the Great Dislocations hy which the Cumbrian Mountains became 

 separated from the Central Carboniferous Chain, ^c. 



The internal movements which produced the derangement of the groups 

 of strata described in the preceding section were succeeded by a long period 

 of comparative repose, during which our whole carboniferous series was elabo- 

 rated. Had our island been laid dry immediately after that period, without any 

 change of relative position among the great formations, the Cumbrian moun- 

 tains would have appeared as a cluster of ancient rocks rising out of a great 

 carboniferous plain; extending north and south from the border of Scotland to 



