Prof. T. G. Bonney — North- Western Chamwood Forest. 551 



If this rock is an agglomerate, so are they ; if they are igneous rocks, 

 so is it; and I am now compelled to abandon the former and adopt 

 the latter conclusion. 



This, however, makes it impossible for me to accept the view 

 expressed by my friend Professor Watts in his excellent account of 

 Charnwood Forest. 1 Arguing against our view that the Peldar and 

 Sharpley porphyroids might be lavas, he says that an excavation at 

 Bardon Hill had disclosed porphyroid exactly like that of Peldar Tor, 

 "intrusive into the Bardon rocks. The junction was irregular, the 

 margin of the porphyroid was chilled and fine-grained, and the edge 

 of the Bardon ashes was hardened and turned red." 2 But in 1887, if 

 not earlier, I had examined junctions of the two rocks and had seen, 

 as already stated, lumps of the Peldar porphyroid, a few inches in 

 diameter, completely enclosed in the ordinary Bardon rock. 3 Of these 

 relations I have full notes, written on -the spot, and possess a specimen 

 showing a junction of the two rocks. Last July I saw a similar lump 

 of Peldar porphyroid, fully seven inches in diameter, embedded in 

 the ordinary Bardon rock, in which one could detect half-digested 

 remnants of the other. 4 Another large specimen showed, as I had 

 already seen in the quarry, a sharp junction between the two rocks, 

 with no change in the ordinary structure of the porphyroid; which, 

 however, taken as a whole, is not always quite uniform in its 

 texture. Thus, though it may be an intrusive of some kind, a sill or 

 a rather thin laccolite, 5 I am convinced that it is anterior to the 

 Bardon Hill rock. 



The second section, quoted by Professor Watts to prove the intrusive 

 character of the Peldar porphyroid, I have not seen, because it was 

 exposed in the excavation for the Blackbrook dam, which was 

 undertaken some time after we had given up work on the Forest. 

 That showed the porphyroid to be intrusive in " rocks of the Black- 

 brook stage". But as these underlie the Maplewell series, the 

 porphyroid, even if it were a lava at Bardon, might very well be 

 intrusive into them, for its texture, if it be not that of an ancient 

 lava, must, I think, indicate consolidation at no great depth from the 

 surface. 



We had not sufficient time at our disposal to examine the whole of 

 that part of Batchet Hill 6 which we formeidy considered to be 



1 Geology in the Field, p. 770; also ch. ii in Mem. Geol. Surv., Expl. 

 Sheet 141 (C. Fox-Strangways), p. 5. 



2 Loc. cit., p. 776. 



3 Supposing this to be pyroclastic, I interpreted the other as a fragment 

 ejected in advance of a lava-flow (represented by the Peldar porphyroid) ; but 

 in any case such a relation makes it in the highest degree improbable for the 

 latter to be the intruder. 



4 For the preservation of this, which (with the second mentioned) is now in 

 the Sedgwick Museum, I have to thank Mr. Grant. The only difference 

 between it and the specimen collected by myself is that the ' Bardon ' rock in 

 the one case is greenish, in the other purplish in colour, which, as said above, 

 may be disregarded. Under the microscope they are identical. 



5 I have never detected any hardening of the Bardon rock at the junction 

 with the Peldar porphyroid, and doubt whether the redness mentioned can be 

 interpreted as a contact phenomenon. 



6 A notice of it is given : Q.J.G.S., vol. xxxiii, p. 777, 1877. 



