338 EEV. E. HILL AND PEOF. T. a. BONNEY ON THE 



glassy trachyte, indications of a fluidal structure being still dis- 

 cernible. Among these (besides the above microliths) occur very 

 angular fragments of quartz and a few of felspar crystals. 



At Upper Blackbrook, on a ridge, are beds containing plenty of 

 visible quartz grains, and small fragments of a decomposed, whitish, 

 very compact felsite. On Ives Head, and east of Finney Hill are coarse 

 grits, the grains being principally decomposed felspar or felsite, as 

 if waterworn volcanic material. Some beds, as on the west side of the 

 bed of the old E-eservoir, are of finer material, compact flinty slate. A 

 greenish mottled variety occurs in the garden of the farm-house by 

 the isolated outcrop near Charley Wood. It is an ashy grit, seen, 

 \inder the microscope, to consist of rather rounded grains of felspar 

 with some quartz, and numerous fragments the exact nature of 

 which it is hard to determine; but some certainly seem to be 

 trachytic lapilli, and the whole is not improbably detritus from 

 a trachytic volcano. One of the quartz grains contains a relatively 

 large irregular enclosure which is almost certainly a devitrified 

 glass. 



We do not, with our present knowledge, feel in a position to corre- 

 late all the outcrops. The series forms a well-marked base to the 

 Charnwood rocks ; and the similarity of outcrops on the same strike 

 seems to show that there is little disturbance by cross faults. On the 

 other hand we have more than once suspected some repetition of beds 

 by strike-faults, particularly at Blackbrook. There are arguments 

 both for and against this view. 



The beds in this northern region on the east side of the 

 anticlinal have hitherto been supposed to differ entirely from this 

 Blackbrook series. This view we accepted in our former notices. 

 Bat when we came to examine them more minutely, it appeared 

 that with some differences they had also many common characters. 

 At Short Cliff and some other points green slaty rocks are found closely 

 agreeing with some of the Upper-Blackbrook beds. At the Whittle- 

 Hill quarry and to the west of it are whitish ashy-looking fine grits 

 or gritty slates, whose materials recall the white decomposed felsitic 

 fragments of Upper Blackbrook. The rock of Moorley Hill, where 

 ■two large quarries are opened, is externally very different ; yet, 

 under the microscope, even this appears to have affinities with the 

 rest. Here are dull greenish banded grits, some beds being very 

 fine. The microscope shows the coarser rock to be composed of 

 angular and subangular fragments of quartz, felspar (both orthoelase 

 and plagioclase), with rock-fragments, some appearing to be tra- 

 chytic, and one showing very distinct traces of fluidal structure. 

 There is iron peroxide, some decomposed ilmenite, and a good amount 

 of viridite ; and the felspathic constituents are much decomposed. 

 The materials have probably been arranged by water. 



An outcrop about half a mile west of this, seemingly of the lowest 

 beds on the east side of the anticlinal (a quarter of a mile south of 

 the east end of Whitehorse Wood), shows soft ashy grits and fine 

 slaty rock, some of the latter being very like some Blackbrook 

 varieties, while the other is akin to Moorley Hill. Microscopically, 



