175 



upheave the strata with equal dips on both sides, if estimated by a plane, as 

 A B, at right angles to the axis, yet as there wdll always be a tendency in the 

 denuding agent to reduce this inclined plane to a horizontal plane, and as 

 it is with reference to a horizontal plane that dips are measured, we may 

 necessarily expect steeper dips, as CAD, on the side toward which the force 

 points, and gentler dips, as C D A, away from it. It may be noticed by the 

 way, that this inchnation of the axis will be seen presently to have some 

 bearing on the question of the clean denudation of the vaUey of Woolhope, 

 and to have determined the future river-system. A comparison of the dips 

 at Cherry HiU, near Fownhope, and Tari-ington Common, being the ends of a 

 section free from important faults, will illustrate the principle here set forth. 



In Fig. 2 a section has been given of the "Woolhope valley in its longest 

 stretch. This must be regarded rather as an illustration of the history and 

 process of the upheaval, than as the production of an accurate sui-vey. The 

 dotted lines represent the Uiiper Silurian beds, as they would have dipped 

 from the May Hill district, had there been no "Woolhope valley of elevation. 

 The horizontal line marks the present approximately plane surface of the 

 ground in the valleys of the 'V\'ye, Frome, and Leadon. It is at Gorstley 

 Common that the upheaving force first indicated its intention by a protrusion 

 of the uppermost Silurian beds, and from this point an irregular broken anti- 

 clinal ridge, seldom exposing strata below the Upper Ludlow, runs up in a 

 general N.W. direction for five miles. This ridge has not caused any very 

 marked geographical feature in the counti-y, the junction line being frequently 

 obscui-ed by trees ; its general bearing, however, may be seen from many points 

 on the Old Eed Sandstone ridge that runs parallel to it from Linton to 

 Yatton ; IMuUiampton Farm House, near Upton Bishop, may especially be men- 

 tioned as affording a good view of it. So far, we have had but a mild preface of 

 the energy of this force ; it would seem to have moved too fast horizontally to 

 have had much effect vertically ; but henceforth we can trace a fuU display of 

 its irresistible power; the Ludlow rocks are rent asunder, and the 'Wenlock 

 strata appear; these also in their turn suffer the same fate, pushing back as 

 they break the Ludlow rocks that overlie them, and being pushed back them- 

 selves by the Upper Llandovery beds, with whose appearance on the surface 

 ends the Woolhope upheaval. "We have been compelled to represent in Fig. 

 2 the axis of elevation as mo^dng continually in the same plane ; it seems 

 probable, however, that it twisted considerably in its coiu-se, being finally 

 turned — as far as can be judged from the dip of the beds, according to the 

 princiiile indicated in Fig. 1— in the direction of Mordiford. 



We may here make a calculation of the height to which the Upper 

 Llandovery beds that fomi the dome have been raised by the upheaval. It 

 is evident from an examination of Fig. 2, that this is the sum of the three 

 following quantities : — 



