HARKER : NORWEGIAN RHOMB-PORPHYRIES. 
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with the felspar, tending to form a rude graphic intergrowth, 
bespeaks a primary origin for the whole. The augite, very faintly 
coloured in the thin slices, is in rounded or irregular crystal-grains, 
which, however, must belong to an early stage of crystallization, for 
they are sometimes enclosed in the porphyritic felspars. This 
remark applies also to the two remaining constituents, viz., imperfect 
crystals of magnetite and little hexagonal prisms of apatite. 
We clearly have to do here with a quartz-rhomb-porphyry, 
a rock of more acid composition than the common types. A specie 
men of a more basic type, a plagioclase-rhomb-porphyry, I have also 
examined from the Holderness boulder-clay. Doubtless further 
search may be expected to reveal the nepheline-bearing rock too, 
and to add varietal forms under each of the four heads specified. 
The student of igneous rocks in East Yorkshire, while lacking 
material from the "solid" geology of his district, has an inexhaustible 
store-house open to him in the spoils of the Norwegian ice-sheet. 
