It will be most convenient to describe the geology of the Arctic Islands by the formations which are to be found there, which are the following:—
- The Granitic and Granitoid Rocks.
- The Upper Silurian Rocks.
- The Carboniferous Rocks.
- The Lias Rocks.
- The Superficial Deposits.
I shall describe these successive formations briefly, and add a few remarks of a theoretical character, to indicate the important inferences which may be drawn from the facts respecting them made known to us by M'Clintock's discoveries.
I.—The Granitic and Granitoid Rocks.
These rocks form a considerable part of North Greenland, on the east side of Baffin's Bay, and constitute the rock of the country at the east side of the island of North Devon, which forms a portion of the coast-line of the west of Baffin's Bay, and the north side of the entrance into Lancaster Sound.
1. Whale Fish Islands, lat. 69° N., are composed of a very fine-grained, flaggy, black mica schist, composed of black mica in very small plates, occasionally putting on a hornblendic lustre, and minute grains of quartz interstratified with the mica. The softer varieties are cut by the natives into grissets and cooking utensils of various shapes, some of which resemble the cambstones found in Ireland, which are made from a kind of potstone, abundant in parts of the County Donegal.
2. Upernivik, lat. 72° N., Greenland.—This district is famous for the occurrence of large quantities of plumbago, which is found in a metamorphic rock of the following character. Fine-grained, amorphous, granitoid rock, composed of minute particles of grey quartz; a honey-colored felspar of waxy lustre, of unknown composition; minute particles of red semitransparent garnet, of conchoidal fracture; and small particles, with occasional large nests, of plumbago. The plumbago occurs both amorphous, and in long acicular crystals. Sometimes the rock becomes of coarser texture and more crystalline, and the yellow color of the felspar gives place to a greenish tinge; and it sometimes also becomes a felspar of perfect cleavage, semitransparent, and white. The dodecahedral crystals of garnet reach the diameter of one inch.
The general character of the rocks near Upernivik is different from that of the rock in which the plumbago is found; they consist of a fine-grained black mica schist, with very little felspar or quartz, and intersected by thin veins of elvan composed of quartz and white felspar. The cooking utensils of the natives are made from this fine schist, in preference to any other description of rock.
3. Woman's Islands.—These islands, off the west coast of Greenland, are composed of a garnetiferous mica slate, formed of black mica in layers, with alternating plates, composed of white felspar and quartz, and filled with fine garnets, rose-colored, vitreous in fracture, and transparent.
4. Cape York, lat. 76° N., Greenland.—This cape is composed of a fine-grained granite, consisting of quartz, white felspar, with minute specks of a black mineral, of pitchy lustre, composition not yet determined.