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In all the rocks are talcose and show a sort of conglomerate of quartz pebbles, in some cases water-worn and in others angular, bedded in a mixture of quartz and granite detritus. This has in the three areas undergone varying degrees of pressure, and has been upheaved at different angles. In some cases the pressure and heat have been so great that the rock assumes a distinctly gneissic character.
Unlike the region of the Ferrar Glacier and New Harbour, the coast to the north of C. Bernacchi runs on in a succession of rounded bays fringed with low ice walls. At the headlands and in irregular spots the gneissic base rock and portions of moraines lie exposed, offering a succession of interesting spots for a visit in search of geological specimens.
An immense volume of water precipitates itself over the rocky ledge, and under favorable conditions the roar of the cataract can be heard for twenty miles. Below the Falls, the river, turning to the southeast, pursues its maddened career for twenty-five miles shut in by vertical cliffs of gneissic rock, which rises in places to a height of four hundred feet.
If it has taken this length of time for the Niagara Falls to make their way back a distance of seven miles by the erosive power of the water acting on a soft shale rock supporting a stratum of limestone, the immensity of time involved by assuming that the Grand River cañon was formed in the same way is so great that the mind falters in contemplating it, especially when it is recognized that the escarpment of the Labrador Falls is of hard gneissic rock.
Considering the immense distances between these several points, and their different heights, it appears to me infinitely more probable, that this similarity has resulted not from contemporaneousness of origin, but from the similarity of the rocky framework of the continent: it is known that in Brazil an immense area consists of gneissic rocks, and we shall hereafter see, over how great a length the plutonic rocks of the Cordillera, the overlying purple porphyries, and the trachytic ejections, are almost identical in nature.
We had two lectures last week the first from Debenham dealing with General Geology and having special reference to the structures of our region. It cleared up a good many points in my mind concerning the gneissic base rocks, the Beacon sand-stone, and the dolerite intrusions. I think we shall be in a position to make fairly good field observations when we reach the southern land.
A huge mass of the veinstone holding abundance of this mineral is exposed, whence it may be plentifully obtained in excellent crystals. Pyrites. White and yellow iron pyrites are abundant in the gneissic rock adjoining the limestone, and frequently very fine, perfect crystals may be found handsomely dressed upon the rock. There is no particular portion of the quarries in which they abound.
Foote in the same order, i.e., from south to north, and he tells us that the auriferous localities in this group occur all in small detached strips or patches of schistose rock scattered over the older gneissic series. Mr.
Foote informs us that the chief gold-yielding rocks of Southern India belong to one great geological system, to which, from the rocks forming it occurring very largely in the Dharwar country, he two years previously gave the name of the Dharwar System, as he saw the necessity of separating them from the great Gneissic System, with which they had formerly been grouped.
The spaces between the grains, which are intact, are filled with a confused mass of peripherally granulated minerals, in which strain shadows are very prominent. The rock has been derived by dynamic metamorphism from a basic igneous rock. 4-Biotite Granite Gneiss. Eighteen miles above mouth of Nascaupee River. A fine-grained rock of gneissic structure having a faint pink color.
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