26 PROF. T. G. BONNET ON THE NARBOROUGH DISTRICT. [Feb. 1 895, 



high road and a little nearer the village, specimens resembling the 

 coarse granitoid rock, sent to us, as mentioned in our third paper, 

 by Mr. W. J. Harrison. 1 It appears to occur in either the ordinary 

 rock or a slightly darker variety of it, more like a node than an 

 included fragment, for the boundary is not quite sharp, and it forms 

 masses sometimes measuring 2 or 3 cubic feet. 



As my descriptions in 1878 were made from a small number of 

 slices, I have now had more specimens prepared. 2 At Enderby village 

 I have examined the rock of ' Rawson's Pit ' and that of the ' Enderby 

 Company ' lower down the hill on the north ; at Stony Stanton I 

 have slices from pits, one north of the village and another south-east 

 of it ; in the Sapcote massif (doubtless part of the same) from an 

 old pit, north of the road on the east side of Sapcote village, and at 

 Croft Hill, from the pit at the southern end. All these show the 

 same general characteristics with those described in the former 

 paper (excepting, of course, the specimens from the Lower Enderby 

 and the Narborough quarries). The differences between them are 

 so slight and unimportant that any minute descriptions are not 

 worth printing. Here a porphyritic structure maybe slightly more 

 distinct ; there the groundmass may contain a little more or a little 

 less quartz, or be a trifle coarser or finer in grain ; sometimes the 

 hornblende may be better preserved (the biotite is generally altered) 

 or be more completely idiomorphic (as in the old pit near Sapcote) 

 than at others. The groundmass consists of small prisms of felspar 

 (decomposed and reddish, mostly, I think, orthoclase) with inter- 

 stitial quartz. 3 The porphyritic felspars, commonly about "05 to 

 •08 inch in diameter, are fairly idiomorphic ; their state of pre- 

 servation varies ; they are usually plagioclase, often zoned, partly 

 oligoclase, partly labradorite, so far as one can conclude from their 

 extinction-angles. A yellowish mineral resembling sphene, probably 

 arising from the decomposition of ilmenite, is sometimes present, 

 also a little epidote. A colourless augite can be recognized in a 

 specimen from Huncote, and the mineral may be present in others, 

 but certainly is not now common. I have not identified any rhombic 

 pyroxene. 



The pit at Barrow Hill has been somewhat enlarged. I believe 

 that, as suggested in the last paper, only one kind of rock is quarried 

 here ; the colour-change being mainly, if not wholly, due to weather- 

 ing. The rock which crops out in a field roughly west of the 

 windmill seems to me slightly more porphyritic than that in the 

 pit on the opposite side of this building ; Avhile that in an old 

 shallow working about 300 yards away to the south-east appears in 

 places rather more compact and redder than either. I have examined 

 it microscopically, but the difference from the earlier specimens is 

 so slight as to be unimportant. The rock of Barrow Hill is certainly 

 rather less quartzose than that of the other outcrops, and the 



1 Quart. Journ. Geol. Soc. vol. xxxvi. (1880) p. 349. 



2 Altogether twenty-one slices. 



3 Apatite is not uncommon in some slices ; iron oxide, generally black, occurs 

 in small grains; a zircon is present in the Sapcote slide. 



