On Terminal Curvature in the South-western Counties

Abstract

More than two years ago my attention was drawn to this subject by the perusal of a paper by Mr. Mackintosh in vol. xxiii. of the ‘Quarterly Journal.’ Having in the interim neglected no opportunity of studying the phenomena in question over a large area, I arrived at conclusions adverse to those advocated by Mr. Mackintosh; so that the object of this paper is twofold :—first, to controvert Mr. Mackintosh9s opinions; secondly, to put forward more tenable explanations. To carry out this object thoroughly is impossible without considering the Pleistocene history of Devon, c but as the wider subject is reserved for a future communication, I shall here only touch on it as briefly as possible. Part I. Mr. Mackintosh suggests four explanations of the instances of terminal curvature described in his paper*. They are as follows :— 1st. “Land-ice filling up the basin of the Bristol Channel” and travelling southward. 2nd. Floating ice, in bergs or in “any other form.” 3rd. “A swift oceanic current exerting a pressure on the underlying slates by means of a forcible drifting forward of detritus.” 4th. “A still more violent rush of waters caused by a sudden upheaval or depression of the land.” The first of these alternative solutions finds most favour with their author. I do not deny its applicability to some instances of terminal curvature within three or four feet of the surface in glaciated districts; but in the South-western Counties, where evidence of