96 Prof. Sedgwick, on the Carboniferous Chain 



and ranging in a direction about west by north, cuts through the junction of 

 the carboniferous and greywacke chains. 



The highest strata of Casterton High Fell are of millstone grit ; and 

 desending in the direction above indicated, we cross every bed in regular 

 succession down to the strong post limestone (No. 5. general section). But 

 at a place called Short Gill, on traversing the line of the great fault, we find 

 that all the lower groups, including the Scar limestone, have been torn up 

 from the foundations of the mountain, bent into a saddle, and afterwards 

 jammed between the edges of the horizontal beds and the steep face of the 

 neighbouring greywacke ridge. 



In order to explain this appearance, we must remember — that the grey- 

 wacke chains existed in some form or other before the deposit of the carbo- 

 niferous system — and that the beds of this system, before their elevation, must 

 have abutted against a series of inclined planes presented by the submarine 

 portions of the old greywacke chain. During a subsequent elevation, both 

 the greywacke and carboniferous systems appear to have been violently acted 

 on at the same moment, and a great strain, accompanied by a relative vertical 

 movement, to have taken place all along the plane of their junction. But a 

 relative vertical movement of the inclined flanks of the older mountains might 

 not only break off the ends of the carboniferous strata abutting against them ; 

 but would also necessarily produce a great horizontal thrust, which may, I 

 think, account for such a curvature of the dislocated masses as is indicated in 

 this section. 



This example has been selected on account of its complexity. There are 

 many places along the line of dislocation, where the lower groups have been 

 torn off, by the pressure of the greywacke hills, from the horizontal system, 

 and tilted up at a great angle, without undergoing any flexures or contortions 

 like those at Short Gill. 



The fourth transverse section (fig, 8.) presents still more complex disloca- 

 tions. It ranges nearly east and west, from the top of Baw Pell to Hebble- 

 thwaite Hall Gill, and thence across the upper part of the valley of Sedbergh 

 to the Howgill Fells. 



The west end of Baw Fell top is, if I mistake not, composed of the second 

 millstone grit (No. 15. general section) ; the inferior groups along the line of 

 section are much concealed under morass ; but several of them may be dis- 

 covered by ascending the different water-courses. The four-fathom limestone 

 and the Mosdale Moor limestone are both well exposed, and the horizontal 

 system terminates with flaggy gritstone and carbonaceous shale, containing a 

 subordinate bed of coal which has been extensively worked. (General Section 



