THE PKECARBONIPEROFS EOCXS OF CHAENWOOD FOEEST. 337 



24. The Peecaeboxiferous Rocks of Chaenwood Foeest. — Part III. 

 Conclusion. By the Eev. E. Hill, M.A., F.G.S., and Professor 

 T. G. BoxNET, M.A., F.R.S., Sec. G.S. (Read May 26, 1880.) 



Contents. 



1. The Northern District. 4. Bardon Hill. 



2. Additional correlations. 6. Fragments in agglomerates. 



3. The district of Sharpley, 6. The Slates. 



Eatchet Hill, and Peldar Tor. 7. Igneous Eocks. 



In our former communications on this region we gave a general 

 description of the northern district. Though some points were 

 worked out in detail, yet less time was devoted to this than to the 

 more accessible districts, and several difficulties remained, on which 

 we hoped that renewed work and wider experience would throw 

 some light. Accordingly, during the last two years we have repeatedly 

 visited the neighbourhood, and added largely to our collection of 

 rocks and slides * ; the present paper contains the results of these 

 studies, which we venture to hope will not be without interest. 



(1) The Northern District. 



In our brief notice of the beds in the Blackbrook and Charley 

 region, as we had paid no minute attention to them, we followed 

 previous writers in calling some of them quartzites. As will appear 

 from the descriptions below, no rock here can properly be called a 

 quartzite ; and we propose to denote this important group, apparently 

 the lowest visible among the Charnwood beds, simply as the Black- 

 brook series. The normal rock is a pale-greenish sandy -looking 

 rock, commonly much stained with ferrite from the Trias, more or 

 less finely banded, and somewhat cleaved. It is best seen near the 

 Blackbrook toll-gate, on the Ashby and Loughborough road, and here 

 is of a pale greenish grey colour, with reddish stains, somewhat com- 

 pact and decidedly like a quartzite. Under the microscope it exhibits 

 a clear matrix full of very small microliths (belonites &c.) of a very 

 pale green colour, with irregularly disseminated subangular "grains 

 of quartz, and some felspar, now and then stained with ferrite. The 

 microliths are probably a pale fibrous variety of hornblende. With 

 crossed Nicols many parts of the slide show a cryptocrystalline 

 structure, resembling that of a devitrified rhyolite, distinct frag- 

 ments of which rock appear to be present. From the structure we 

 should suspect that the rock originally was largely composed of a 

 pumiceous dust. The rock by Charley church, which has a general 

 resemblance to the above, and is probably on nearly the same 

 horizon, strongly confirms this view. It is composed chiefly of 

 small fragments, apparently rather angular, but looking as if much 

 compressed, which very closely resemble bits of a rather decomposed 



* More than 60 slides have been prepared, all by Mr. F. G. Cuttell, making 

 the total number examined from Charnwood about 150. 



Q.J. G.S. No. 143. 2 a 



