2. The next rock, which forms numerous mountains in this country, is GNEISS. It occurs very often alternating. with granite, sometimes with mica slate. Its character or texture may be ascertained partly in the cliffs and on the shores, partly by the forms of the mountains. The grani tic mountains are always more decomposed, and therefore more precipitous, presenting very sharp-edged summits ; the summits of the gneiss are more flat and round-backed. The texture of the gneiss is thick and thin slaty ; its fel spar generally pearl-grey and pearl-white, seldom flesh red, fine granular : its mica grey, pinchbeck-brown, and blackish-brown: it contains but little ash-grey quartz. The valleys and clefts round the mountains are filled with rhomboidal fragments, many of them of immense size. The smaller fragments were used by the old Norwegians, with mica slate, hornblende-slate, and slaty claystone, to build their houses ; the walls of which, although not ce mented, after a lapse of several centuries, still brave the power of this destructive climate.
Gneiss constitutes one of the most elevated points of this extensive coast, viz. the mountain Kingiktorsoak, situated in the 62d degree of latitude. It is covered with mica slate from the shore to a height of about 1000 feet above the level of the sea, where the gneiss again be comes visible, and continues to a height of nearly 3000 feet. The top of this mountain is similar in shape to the roof of a house, where the ridge is not much elevated. It is entirely free from snow in summer, except a few small spots, where it rests in the hollows of its summit.
The mica slate resting upon the gneiss presents a va riety of beds of hornblende slate, whitestone, (weiss-stein) with small garnets, talc-slate, with common and indura ted talc, potstone, actynolite, and precious splintery ser pentine. The gneiss is traversed with numerous veins of greenstone, varying in thickness from one inch to six feet. The greenstone which occurs in the veins resembles ba salt ; but it is more crystalline in its texture, lighter in its colour, and not quite so hard. Common schorl, tour maline, and precious garnet/ occur imbedded in gneiss. It contains veins of tinstone, accompanied by arsenical pyrites, wolfram, flour, and quartz, in a firth, called Arksut, situated about thirty leagues from the colony of Juliana Hope, towards north-east. The same place is remarka ble for two thin layers of cryolite resting upon gneiss ; and it is the only place where this mineral has hitherto been found. One of these layers contains the snow white and greyish white variety, unmixed with any other mineral. Its thickness varies from one foot to two feet and a half, and it is divided from the underlying gneiss by a thin layer of mica, always in a state of disintegration. The other variety is of a yellowish brown colour passing into tile-red. It occurs along with iron pyrites, liver-brown sparry iron ore crystallised in rhombs, earthy cryolite, quartz, com pact and foliated fluor, earthy fluor, and galena. It is remarkable, that the galena is sometimes coated with a greyish white sulphureous crust, which burns in the flame of a candle with a bluish colour, emitting a sulphureous smell.
These layers of cryolite are situated very near each other, only separated by a small ridge of gneiss, of a thickness of 27 feet : both are washed at high water by the tide, for the most part exposed, the superincumbent gneiss having been removed. The white cryolite, seen at a dis
tance, presents the appearance of a small layer of ice ; small detached fragments have acquired, from decompo sition, the shape of cubes. This mineral is called by the Greenlanders orsuksikset, from the word orksuk, blubber, to which it bears some resemblance. The same name is also given by the natives to white calcareous spar.
3. Mien SLATE is likewise one of the most common rocks in Greenland, and an inseparable companion of gneiss : There are very few instances where they are not found in the vicinity of each other, and frequently in contact. Mica slate forms in this country a very extensive series of insulated mountains, which never rise to a considerable height., and appear generally to rest upon gneiss. Mica slate is frequently visible on the shores, and the gneiss itself forms also very extensive beds in it at Disko bay, where the whitestone also occurs in beds. The Green landish mica slate abounds in mica ; it is generally thin slaty, and only thick-slaty when the quartz prevails. Sometimes it has an undulating aspect ; but when this is the case, it passes into primitive clay slate. The mica of this mica slate is mostly greyish-black and pinchbeck brown, passing into brownish black, seldom silver-white. Its quartz is pearl-grey. It is sometimes mingled with nodules of pearl-grey felspar, from the size of a pea to that of an orange, and this gives it the appearance of gneiss; but they may be easily and accurately distinguish ed, as the mica-slate presents a surface perfectly continu ous, and easily separable in the direction of the plates of the mica. The strata dip towards north-west. Mica slate also occurs in beds in various parts of this country. One of the most remarkable, most interesting, and most extensive,, is that in the firth Kangerdluarsuk, in the 61st degree of latitude, in the district of Juliana-Hope. It ex tends about five miles in length, and four miles in breadth ; its thickness varies from six to twelve feet ; and it con tains, besides felspar, which is its principal constituent part, hornblende, augite, actinolite, sahlite, garnet, and that new mineral which has been analysed by Dr Thomson and professor Eckoberg, called Sodalite. It is of pale and apple-green, leek-green, greenish white, and pearl-grey colour, partly massive, partly crystallised. Another mine ral, which has not yet been analysed, occurs also with the sodalite : it is of a peach blossom red and purple-red colour. On the shore, the underlying gneiss is visible in several places. In'the superincumbent mica slate, granite is found of very fine texture, partly in reins, partly im bedded. Calcareous spar and fluor occur in veins, both of which are sometimes coated with a thin crust of chal cedony, also galena in small veins. Blue phosphate of iron in detached pieces is found on the shores. The mica slate is generally decomposed and iron-shot, where the graphite is imbedded. In the firth of Arksut, a bed of very fine granular limestone is found in mica slate, which resembles the Carrara marble. The beds which occur in this rock on the mountain Kingilktorsoak have been already mentioned. Hornblende slate, forming beds in mica slate, is found in many places.