C—ll

46

Nature of the Rocks. On the western coast-line the rocks from Gulches Head are granite to and beyond Red Head. To the eastward the granite is overlain by coarse or finer conglomerates forming the basement-beds of the coal-bearing series. (Slates occur within the area of Gulches Head Peninsula, but these lie further to the north, along the western shore of South Port.) The conglomerates at the base of the coal-bearing series are succeeded by sandstones, and sandstones and shales with small seams of coal, one seam varying from 2ft. 7in. to 4ft., and the series is again closed by conglomerates of coarse pebble-beds, as seen at the inner point of Gulches Head. On these granite and coal-bearing rocks there rests indifferently a considerable deposit of tough clayey gravel, evidently of glacier origin, which has clearly yielded under the action of denuding and reassorting agents the bulk of the material forming the younger and more auriferous series of gravels. These morainic deposits are not naturally exposed at many places, and, for the most part, are seen in the working-faces which have been opened out in different parts of the claim. They contain a considerable proportion of well-rounded stones, besides the angular material characteristic of such deposits. The clay and finer parts of the deposit contains scarcely any gold, so far as yet ascertained, nor is black sand present to any extent, but iron-pyrites are abundantly distributed throughout the mass. Resting on these glacier deposits, and next in sequence, comes the auriferous gravel. This is a comparatively free, gravelly, or sandy wash, which, under a moderate head of .water, should pull down and be removed with ease as rapidly as prudent to put it through the tailrace. What the average thickness of this wash is it might be difficult correctly to say, since the faces opened out are not sufficient to determine the point. Professor B. Hooker estimates their thickness at an average of 30ft. I think this a fair and not too high an estimate for some parts of the area. The manner of the formation of these gravels was by the action of the sea breaking up and reassorting the morainic gravels that underlie, which operation was continued during a sinking and subsequent elevation of the land, the effects of the latter movement being the more apparent. Without doubt the glacier deposits, from which the auriferous gravel has been derived, were at one time continuous with like deposits on and over the greater part of Coal Island; but this connection was broken during the periods of depression and upheaval and while reconstruction of the glacier-drifts was being carried on. On what is now the land area bounding the channels of entrance to the inlet the* material has been swept seaward to form deposits at lower levels, or in different parts has been thrown back upon the coast-line. The middle and south-western end of Coal Island shows sandstone cliffs rising to a considerable height above sea-level, but at Price's Beach the glacier deposits yet pass under the sea-level, and this, wasting away more rapidly than the hard grit and sandstone rocks at each end of the beach, accounts for the indentation that here takes place, and also for the abrupt character of the terrace-face. As the eastern abrupt slope from the terrace at the back of Price's Beach has been moulded and formed subsequent to the laying-down of the gravels at higher levels, down the steep slope facing the shore, the reassorted gravels probably do rest on a series of flat ledges carved out of the glacier-deposit, the upward movement probably being intermittent in character; and even if the land rose gradually and regularly a tendency to cut ledges in the morainic gravels would display itself, as the size or compactness of the material affected might vary at different levels. The top of the terrace at the southern end of Price's Beach is exactly 100 ft. above sea-level, at the northern end of the beach it is considerably more, say, 140 ft. From the southern end there is a gradual slope westward to the sea at the mouth of Back Creek, where the terrace-lands terminate at about 25ft. above tide-mark. Between the northern end of Price's Beach and a point from the sea in the valley of Back Creek corresponding or slightly exceeding the length of the eastern terrace-face the slope is also to the westward, but, owing to the lower level of the southern end of the sloping tableland, the direction of the maximum fall is to the south-west. North of the southwest slopes of Round Hill the valley of Back Creek is bounded by ranges of hills to the east and west. It is reported as being in the upper part of moderate width and so flat as to afford exceptionally favourable sites for the construction of dams, more especially at one place where, as reported by Professor Hooker, a dam of very considerable capacity might be constructed at a comparatively trifling cost. Younger than the reconstructed gravels, yet at a higher level and older than the beach-sands of the present day, are deposits of black sand which contain gold. These form a narrow terrace towards the southern end of Price's Beach ; but towards the north the black-sand deposit clings to the steep slope descending from the break of the high terrace to the north-west. These sands are auriferous and cover a pavement of large boulders or one or two feet of finer wash; the whole at the northern end of the beach rests on morainic matter, or on coal-rocks. Auriferous Character of the Gravels ivithin Block I. The highest and most northerly working-place which has been opened out in these gravels is not now being worked. Professor B. Hooker tested the ground at various places, and reported the finding of such prospects as might well lead to sanguine hopes of a rich return, even with the limited water-supply that was at that time available. Water was brought on to the ground, and enough of this north part of the high level washed away to show that the gravels here would scarcely pay, and did not, as regards the quantity of gold, correspond with the prospects obtained at the surface. At a lower level, on the slope of the same ridge, another opening was made, but was left, and another face was partly opened in the next gully to the south. At this place gold is distributed through the gravels over a vertical height of 25ft. from the bottom. Some prospects taken here showed a number —five to twenty—of colours of fine gold ; and in this face, also, I am satisfied that coarse gold is to be found, though I saw none in the prospects washed from the face.