558 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [JunC 20, 



and had carried forward with it the surface on which it rested. A 

 few pebbles, which had become engaged in the claj, had received a 

 considerable amount of polish. The weathering extended about as 

 far as the clay had been moved. A specimen of this clay is depo- 

 sited in the Society^s Museum. Similar instances were seen by Mr. 

 Boyd Dawkins and myself at Walton-on-the-jS'aze, and by Professor 

 Liveing and myself at Aldborough. 



It is very desirable that the trail should diligently be searched for 

 organic remains. As yet I have never seen any vestiges of such, 

 either animal or vegetable, within it. It will constantly be found 

 filled with roots ; but that is owing to its inviting theii' presence by 

 the subterranean drainage caused by the usual clayey lining of the 

 bottom of the furrows. 



As far as I have had opportunities of examining the furrows, I 

 have noticed that they are largest and most numerous in the neigh- 

 bourhood of valleys, and are either parallel or inclined at a small 

 angle to them. If, as I believe, they are connected with the pheno- 

 mena of denudation, this is what we should expect. 



If there ever was formerly a universal spread of trail over the 

 general surface of the land, it has now disappeared, and the only 

 remains of it are to be found in the furrows, which lie deeper than 

 the latest general denudation has extended. 



There can be no doubt that these furrows, with the trail which 

 they contain, are older than the warp, and that their contents have 

 contributed to form the warp or general subsoil ; and thus we see the 

 reason why the surface-soil sometimes varies so remarkably over 

 limited areas ; for these patches of trail are not universal, and where 

 they occur they influence the composition of the soil to considerable 

 but not to great distances. 



There can, I think, be not much doubt that there was a time 

 when our country was comparatively, if not entirely, bare of the pre- 

 sent covering of vegetation ; for the denudation which formed these 

 furrows can hardly be supposed consistent with a clothing of turf or 

 forest. When the more severe climatal conditions, whatever those 

 may have been, which conduced to the denudation had passed away, 

 the country would become gradually covered with vegetation, and 

 the work of rain and rivers and frost, under their more ordinary 

 conditions, would commence to modify the form and state of the 

 surface. 



Let us now consider the final preparation of the warp. Conceive 

 the face of the country, as the denuding forces left it, consisting of 

 the bare rock, thinly covered in places by the trail of material left be- 

 hind by that agency, and in places occupied by furrows, or shallow 

 hollows, filled with similar stuff. This is the foreign material to be 

 incorporated with the subjacent rock to form the warp. 



Atmospheric causes have operated from that distant day to the 

 present in bringing about the result. Rain and, during drought, 

 winds have tended to spread the finer materials of the surface. 

 Frost has affected the envelope as far as it could penetrate, mixing 

 the natural rock with the adventitious matters. After vegetation 



