Nov. 1889. ROCK SPECIMENS COLLECTED IN NORWAY. 
265 
As might be expected they almost all belong to the highly 
metamorpbic rocks which go by the names of gneiss and 
schist. Of these there are several varieties. On the one hand, 
there are specimens which in the two or three inches square 
which their surfaces afford are not distinguishable from 
granites, as they show none of the foliation which characterises 
the gneisses. From these there is a gradual passage to the 
most intensely foliated specimens which have plainly been 
submitted to immense shearing and rolling strains. The 
schists are mostly of that stage of formation in which the 
original constituents are not utterly lost, but only crushed, 
twisted, and utterly deformed, while secondary micas have 
formed in discontinuous layers among the fragments. 
These crushed and rolled rocks have exactly the aspect of 
many of those from the N. W. Highlands, with the elucida¬ 
tion of which the name of Professor Lap worth is so closely 
identified. There is a pure hornblendic gneiss which almost 
absolutely resembles some specimens of the grey Hebridean 
gneiss of the Scotch district. 
Of these rocks I have cut one section—from a reddish 
gneiss rock which yet showed by its generally rather dull 
aspect and the obvious knots of felspar that it had not arrived 
at the fully recrystallised stage of metamorphism. 
Examined microscopically this structure is still more 
striking, and the use of polarised light shows almost every 
felspar grain crushed and twisted, and in by far the greater 
number of cases affected with the peculiar cross twinning 
which is characteristic of microcline, but which has been of late 
suspected as being specially developed where felspar crystals 
have been subjected to great crushing. It will be remembered 
that Professor Judd has proved that the ordinary twinning so 
frequent in plagioclase is often confined to those parts of a 
crystal which have been strained by being bent or crushed, 
and that even in quartz changes of molecular structure 
equivalent to twinning have been brought about by the same 
means. 
With this specimen I should like you to compare one 
from the pebble beds which are so largely developed locally. 
At least it is really from the upper gravel beds at Catspool, near 
Alvechurch, but I have no doubt it is derived from the washing 
of the older pebble beds. It has a very similar appearance, 
is, however, almost altogether felspathic, and shows none of 
the eyes of larger felspar grains, but a very curious lineation 
perpendicular to the foliation (which is much more marked 
in the hand specimen than in the section) is apparent, giving 
the look of a section of wood. This seems to be due to the 
