20 



PROF. T. G. BONNET ON THE 



[Feb. 1896, 



of a dull green, rather strongly pleochroic hornblende, in somewhat 

 irregularly-formed crystals, commonly much speckled with minute 

 and elongated specks of iron oxide. Some larger granules of the 

 latter mineral occur, with a little rutile and possibly pseudobrookite. 

 Besides, there are a few isolated grains or granular patches of a clear 



Fig. 2.— Eye of hornblendite, included in banded hornblende-schist. 

 {Northern side of Porthoustock Gove.) 



a = banded hornblende-schist. 



b = coarsely crystallized hornblende. 



mineral : this has rather a high refractive index and low polarization- 

 tints for a felspar, an extinction, I think, oblique (it is difficult to get 

 any line from which to measure), and it may perhaps be a colourless 

 epidote. These inclusions, though on a much smaller scale, recall 

 to mind those which we found so common in Sark. 1 



(b) Inclusions in the Hornblende-schist south of Kilcobben 



Cove. 



Here also the rock is frequently streaked, and instances of 

 resemblances to current-bedding are by no means rare. Near to the 

 northern side of the promontory we found long lenticular masses of 

 rather coarse hornblendic rock, such as is described above, lying with 

 their flat sides roughly parallel with the dominant banded structure. 

 They are seldom more than 2 or 3 inches thick, but are sometimes 

 2 or 3 feet long and almost as wide. 2 From this size they may be 

 found down to little patches, almost streaks. 



(c) Quarry on the descent to Mullion Cove. 



This quarry, noticed in the paper of 1891, 3 was in a better con- 

 dition for study at the time of our visit in 1894. The rock here is 

 generally coarser in structure than any other mass known to us in 

 the Lizard peninsula. Most of it shows a banded structure, which, 



1 Quart. Journ. Geol. Soc. vol. xlviii. (1892), p. 128, etc. ; see also vol. xliii. 

 (1887) p. 324. 



2 In a slice from one of these I find nothing but hornblende, like that described 

 above, and a little iron oxide. But the rock was very difficult to cut, and the 

 slice is a rather thick one. 3 Op. jam cit. p. 479. 



