NORTH-WEST REGION OF CHARNWOOD FOREST. 79 



with Sharpley and Eardon Hill, in rc^^ard to which, as stated at the 

 time *, we had found great difficulty in deciding whether the 

 rocks had been originally ashes or lavas ; that is to say, whether 

 the fragmental structure, which could be dimly traced, had been 

 present from the very first, or had been superinduced. We dis- 

 cussed the question at length, giving, to our best ability, the 

 arguments on each side, and coming to the conclusion that the rocks 

 of Peldar Tor, of Sharpley, and of Bardon Hill were all of pyro- 

 clastic origin. Still, as expressed at the time, this view was not 

 without considerable difficulties, especially in regard to the first and 

 second, and during the following three or four years new factors were 

 introduced into the problem, of which account had to be taken. 



The researches of l^ehman, Heim, and others, coupled with our 

 own work in other fields, indicated that earth-movements were far 

 more effective than had hitherto been supposed in producing breccia- 

 tion and clastic structures in large masses of rock, which originally 

 had been homogeneous or crystalline. Again, increased experience 

 showed lis that from flow-brecciation and other causes a fragmental 

 structure was of commoner occurrence in a true lava than we had 

 expected, and that the general uniformity of character which was 

 presented by the rocks of Peldar and Sharpley over such large areas 

 was very difficult to parallel in the case of tuffs. One thing, how- 

 ever, more than any other made a reconsideration of the question 

 absolutely necessary : we referred in onr discussion to the porphy- 

 roids of the Ardennes as presenting very close resemblances to the 

 Peldar and Sharpley rocks, especially to the latter. These had been 

 examined by eminent geologists, who had discussed their origin, 

 and denied it to be igneous f- Iii 1882, however, one of us was able 

 to visit the Ardennes, and came without any hesitation to the con- 

 clusion that these porphyroids were simply igneous rocks modified 

 by subsequent pressure J. This of course struck away one of our 

 chief supports, and led us to examine the Charnwood district anew. 

 "NVe were the more hopeful of some result, because the publication 

 of the six-inch map made it possible to record our observations with 

 a detail which was impossible on the ordinary one-inch map, and thus 

 to obtain a clearer idea of the form of the areas occupied by these 

 rocks, and of their relation to others in the neighbourhood. Accord- 

 ingly, during visits in the spring of 1887, 1889, and 1890, we 

 carefully re-examined not only all the north-western part of the 

 Forest, but also a few other localities about which we felt some 

 difficulty or were hopeful of additional evidence. 



II. The North-west Region and Bardon Hill. 



1. General Description of the North-west Region. — This district is 

 entirely included within lines drawn through Abbot's Oak (or 

 Greenhill) and the Whitwick-village Quarry (Pinfold Quarry) on 



* Op. cit. pp. 341-348. 



t ' Les Roches Plutoniennes de la Belgique,' <tc. p. 240, 



\ Bonne V, Proc. Geol. Assoc, vol. ix. (1885) p. 247. 



g2 



