Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/213

 described, rises at an angle of 12°. Soon after, the strata change their direction from N.N.E. to east by north, and at the same time acquire an elevation of 36°. Benthal Edge is separated from Lincoln Hill merely by the narrow valley of the Severn, at that place not two hundred yards wide; and the strata of this latter hill have the same direction as Benthal Edge, but their horizontal angle has increased to 45°, and the height of the hill above the level of the Severn is considerably inferior to that of Benthal Edge. Beyond Lincoln hill the strata, as far as they have been explored, preserve the same angle and direction; but their height is not superior to that of the coal-field which they traverse, hence the circumstances of their termination in the neighbourhood of the red sandstone are unknown.

In a geological point of view, the limestone strata above described are remarkably interesting. We see them stretching for several miles, nearly in a strait line, N.E. and S.W. with an elevation not exceeding 9°; and this part may be considered as exhibiting the limestone, with regard to these circumstances, in its original situation. The interval now occupied by the valley of Mar brook points out the direction of a fracture caused by the motion of the whole body of limestone between this brook and the Severn, which has elevated its north-western and proportionally depressed its south-eastern extremity. The narrow valley of the Severn itself points out another nearly parallel fracture, caused by an analogous and probably contemporaneous motion of the strata of Lincoln Hill, by which it is obvious that the present valley of the Severn was formed. With the above unequivocal fact is connected an important object of enquiry, namely, the mode by which the elevation and depression of these beds was effected.

With regard to this question, it may be observed that strata are capable of vertical motion by a force acting either from below upwards,