BARKER : PETROLOGICAL NOTES. 
413 
No. 547, taken near the Matron, High Stacks, at high-water 
mark, is a gneiss of different type and finer texture. It has no 
hornblende, but only biotite, which, besides an ill-defiiied parallel 
arrangement, has a tendency to collect in clusters, which show as 
dark depressions on a water-worn weathered surface. The pink 
felspar of this rock seems to be orthoclase. The quartz is mostly 
confined to lenticular streaks following the general gneissic structure 
of the rock. No. 43 is a grey gneiss of similar characters. 
Rocks such as these last three must have been transported from 
some gTeat metamorphic region of gneisses and crystalline schists ; 
in this case almost certain from Norway. Some of the granitic 
rocks, though not properly gneisses, also give evidence of dynamo- 
metamorphic action. 
Of the many gTanitic rocks, mostly biotite - granites, found 
among our Flamborough boulders, few, except the Shap granite, 
can be certainly set down as British, and the majority are in all 
probability derived from Scandinavian localities. A grey biotite- 
granite from Mr. Lamplugh's collection. No. 114, exhibits no very 
marked characters. Under the microscope [1150] it shows crystals 
of brown, pleochroic sphene, little prisms of zircon, and octahedra 
of magnetite. The brown mica has the usual characters ; the turbid 
felspars are a striated acid plagioclase, with subordinate orthoclase, 
and occasional veining of the one by the other ; while the quartz 
is mostly interstitial, but with a tendency to form mosaic-like patches. 
This rock, excepting a slight bending of the mica-flakes and 
perhaps the veined character of some of the felspars, has, it is true, 
little suggestive of mechanical stress, but other examples are more 
instructive. No. 51G is a gi^ey biotite-granite of fine grain, but 
containing some pinkish felspars up to an inch in length. 
Micro. [1140] This specimen has no sphene, but Kttle acicular 
crystals of zircon and apatite, with octahedra of magnetite, occur 
enclosed by the other constituents. The intensely pleochroic brown 
mica has a slightly oblique extinction, which is sufficient to show in 
many flakes a twinning parallel to the basal plane. The felspar and 
quartz build iiTegular interlocking plates, and a portion of the latter 
mineral is often enclosed within the former in numerous rounded 
