20 PROF. T. G. BONNEY ON THE GEOLOGY 
An examination of Plate I.*, which represents a small portion 
of the cliff face, aided by the smaller diagrammatic figures (fig. 9), 
may, I hope, render intelligible the following extract from my note- 
book, and thus render a lengthy description unnecessary. ‘The 
whole of this bedded mass exhibits a cleavyage-structure, and the 
more gritty bands are squeezed out into long lenticular streaks, as if 
the bedding coincided with the cleavage. Where the gritty bands are 
broadest, there the ends are all ‘frayed out’(fig.9, no. 2); where the 
banding has been fine and rather close, there it has been entirely obli- 
terated andreplaced by thisnew structure of parallel lenticular streaks 
or elongated ‘ eyes (fig. 9,no. 3). Round these the darker part of the 
rock bends, just as the folds of mica in a gneiss pass round the len- 
ticular patches of quartz and felspar. Occasionally, perhaps where 
the materials of the gritty band have been coarser than usual, 
rather larger lumps have been formed, like the ‘eyes’ in an 
augen-gneiss. These are ‘ drawn out,’ as it were, into long flame- 
like ends, with more distinctly indicated central eyes. They vary 
in length from about 1 to 3 inches, and in breadth from % to 4 
inch. In some cases I noticed that the thinner bands were much 
more squeezed out on one side than on the other, like the feather of a 
pen, when the pinnulesare a little separated (fig. 9, no. 4). Commonly, 
during the latest stage of the squeezing-out, there appears to have 
been a slight slipping of one part over another, and a thin film 
of the darker material has been either infiltrated or dragged in 
between ; this aids greatly in obliterating the traces of the original 
bedding and in simulating the aspect of a schist.” I may also 
note that in one or two of the coarser gritty bands in this neigh- 
bourhood (not ‘“‘ teazed ” out as above described) I noticed indications 
of stratule, which might readily be taken as marks of ripple-drifts. 
I came, however, to the conclusion that these were more probably 
indications of a rude cleavage—minute splits along which perhaps | 
a slight infiltration had taken place; they made an angle of about 
15° or a little more with the well-defined and level surface of the 
bed. It may be well to bear this instance in mind, for the struc- 
ture might easily have been mistaken for one of the cases of ripple- 
drift noticed by Dr. Sorby f. 
The peculiar structures described above are, I think, interesting 
as illustrating some of those seen in foliated rocks. Though the Tor- 
cross rock is in no true sense of the word foliated, yet it is often 
an excellent model of one that is foliated. In regard to rocks of the 
latter class it is often difficult to say whether foliation corresponds 
with bedding or is transverse in direction to it, whether it is in- 
dependent, or only a further development of cleavage; further, 
an arrangement of the minerals in lenticular streaks with their 
longer axes parallel is common, especially in gneisses. Ifthe action 
* Copied from a photograph. For this I am indebted to my brother, Mr. 
F. Bonney, who kindly undertook a journey to Torcross to make it. Shingle 
thrown up by a recent storm had buried the best example, but the one which he 
secured is nearly as good. 
T Quart. Journ. Geol. Soc. vol. xix. p. 401. 
