Vol. 52.] BOCKS OF THE LIZARD DISTRICT. 21 



however, here and there disappears, for it passes into a ' spotty ' one. 

 But the general condition of comparatively coarse crystallization is 

 replaced, locally and rapidly, by a finer one ; the latter exactly 

 resembling the normal hornblende-schist, whether banded or 

 1 dioritic,' which occurs elsewhere at the Lizard. Pine-banded and 

 coarse-banded portions may be seen, one within a foot of the other. 

 Of the latter variety, bands, quite | inch thick, consisting almost 

 wholly of felspar, can be traced frequently for more than a foot in 

 length ; bands also, both light and dark, sometimes quite £ inch thick 

 and occasionally more, run continuously for 8 or 9 inches at least. 

 One part of the rock presented a curious resemblance to false bedding, 

 but a closer examination showed that this might be equally well 

 produced by a shearing movement in the mass. In another place 

 the bands were overfolded, and appeared to have become displaced by 

 a * strain-slip ' movement. The latter, no doubt, might be produced 

 after the solidification of the rock, but the general appearance of 

 the former structure and the absence of divisional planes suggested 

 that it was due to a sliding movement, while the mass was still more 

 or less viscid, so that the ruptured surfaces had become cemented 

 during the last stage of crystallization. The irregular and sporadic 

 passage from the banded to the spotty condition also seemed difficult 

 to explain if the former were due to an original stratification of 

 clastic materials, but seemed easily explicable on the hypbthesis that 

 movements had taken place in a magma, after some constituents 

 had separated, but anterior to the complete crystallization of the mass; 

 this had caused the ordinary ' granitic ' structure of a noncrystalline 

 rock to be replaced in many parts by a banded one. 



It has, however, been suggested that these linear structures are 

 due to a yielding — more or less local — in a coarse noncrystalline 

 rock when subjected to pressure. Apart from considerations which 

 I have elsewhere noticed, 1 I had this hypothesis always before my 

 mind and found it inapplicable as a general explanation, though I 

 should admit the possibility of its accounting for a certain ' slabbi- 

 ness ' occasionally perceptible. 2 The effects of dynamo-metamorphic 

 processes, in the ordinary sense of that long word, can be studied 

 at the extreme south and in a more limited area at Porthallow, 

 as described in our former paper, and the conclusions then formed 

 were strengthened on the present occasion by tracing, especially in 

 the first-named district, the gradual change from the normal horn- 

 blende-schist to the pressure-modified ' green schist.' If then the 

 ordinary banded hornblende-schist of the Lizard owes its structure to 

 * dynamo-metamorphism,' recrystallization must have subsequently 

 occurred to such an extent as to destroy every characteristic of that 

 process. To concede this, I may observe by the way, would be fatal 

 to every attempt to implicate the schist and the serpentine in an 

 4 igneous complex,' for the latter rock, as a rule, exhibits no sign of 



1 Quart. Journ. Geol. Soc. vol. xlix. (1893) p. 94, and vol. 1. (1894) p. 279. 



2 But, even if this be due to a very slight shearing, its parallelism with the 

 banded structure and consequent low hade (universal features, so far as I know) 

 are by no means easy to explain. 



