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joins the Aorere about three miles below the junction of the Spey and about half a mile above Brown's. It carries somewhat less water than the_ Parapara in autumn and winter, but during the spring and summer it brings down a much larger body of water, mostly derived from the melting snows on the higher ranges which surround its sources. " From the Quartz Ranges the Aorere receives Finn's, Maori, and Salisbury Streams, all of which rise on the slopes of Pine Ridge. The two former unite a short distance from the Aorere, and the latter runs in a narrow, deep ravine, or gorge from its source to its mouth. " Passing down the valley we next reach the Boulder River, which rises in the wide, open, grassy basin enclosed by the Lead Hill, Haupiri, and Rocky River Ranges. At the lower end of this basin it enters Boulder Lake, from the lower end of which it emerges and then suddenly plunges over a rocky ledge into a ravine several hundred feet deep, through which it flows till it joins the Aorere. A few miles lower down the valley we reach the Little Boulder Stream, which drains the broken limestone area, known as " The Castles." A mile below this we reach the Slate River, by far the most important, if not actually the largest, tributary of the Aorere. It rises on the north slopes of the Haupiri Range, at the foot of the Slate River Peaks. . . . From the south-west it receives Snow's and Rocky Rivers; the former reaches back to the Haupiri Range and is separated from the Slate River itself by Slate River Range, at the north end of which stands Mount Hardy, which attains a height of almost 5,000 ft. From the east the Slate receives Fletcher's and Wakefield Creeks, both small streams, occupying a prominent place in the past history of the Collingwood Goldfield. " Below Slate River the Aorere receives Doctor's and Lightband's Creeks, both of which, with their numerous small branches, were some years ago the scene of extensive alluvial mining operations, as evidenced by the old abandoned workings which meet the eye on all sides. " Below Rockville the Aorere receives a number of small streams from the Whakamaramas, of which the most important is the Kaituna, which has cut a deep gorge through the mountains, and possesses an extended and wide basin or watershed on what may be termed the west side of the main range."* The lower portion of the Aorere Valley is occupied by wide gravel-terraces, forming a triangular space, extending from Parapara Inlet to Collingwood, and from there back to Rockville. From the latter place the terraces extend across the Aorere to the Kaituna, and thence along the course of the Bonny Doon Stream and the foot of the Whakamaramas to the junction of Brown's River. "From the Quartz Ranges to Rockville, and thence seaward to the Parapara Inlet, the country presents the appearance of a great sloping table-land descending from the Haupiri Mountains to the Aorere River. The most striking feature of this sloping table-land is that the slope is not from the head of the valley to the sea, but from the ranges on the south towards the river which flows on the north side of the valley, close under the slopes of the -Whakamarama Range. " Although the surface of the [Collingwood] district is very mountainous and broken, few of the conditions exist that usually accompany the presence of fresh-water lakes. Except Boulder Lake and Lake Otuhei, there are no other bodies of water deserving the name of lake. " Boulder Lake is situated near the source of the river of that name. It is 3,250 ft. above the sea, and is enclosed by Lead Hill and Rocky River Peak. It rests in what is, perhaps, one of the most perfect examples of a rock-basin in New Zealand. The scanty character of the vegetation, and the large surfaces of bare rock exposed on the flanks of Lead Hill, render the study of this interesting lake-basin a matter of comparative ease. The lake itself is about a mile long, and threequarters of a mile wide at its widest part. At its lower end it rapidly contracts, being hemmed in by the descending spurs from the mountains on both sides. It is drained by Boulder River, which, at its outlet, flows through a narrow channel excavated in the solid rock."f The other writers above-mentioned give us little or no account of the general aspect of the country, or a description of the physical features of the parts they had more particularly to deal with; nor, after what has been quoted from Mr. Park's reports, need any further lengthy account be given in this place. General Geological Features. The disposition of the rocks in every part of the Aorere Valley indicates that it was first formed along a line of earth-fracture, trending in the general direction of the present valley, and having its downthrow on the south-east side of the line of rupture. The Upper Aorere Valley is distinct from the lower, and is purely a valley of erosion; hence, subsequent in date to that of the middle and lower parts of the watershed. The great earthfracture that determined the direction of the middle and lower parts runs along the north-west side of the valley, and quite close under the foot of the remarkably abrupt mountain ranges on that side. Its direction is south-west from the shores of Golden Bay to the junction of Brown's River, and thence the same dislocation is indicated across Gouland Downs into the watershed of the Heaphy River. Along the mountains on the north-west side of the valley, Cretaceous, Cretaceotertiary, and Tertiary strata are found at high levels from the Kaituna River to Mount Burnett, and beyond the ridge of the north-east part of the Whakamarama Range they extend considerably to the south-west of the Kaituna Valley. One or other member of the series of younger rocks are also found at different places in the low grounds of the Aorere Valley, close to the steep vertical slope of the range crowned by the same beds, while on the south-east side of the valley the Tertiary and Cretaceo-tertiary beds are found as outliers on the sloping table-land up to heights I,Booft. above the sea. This state of things has not been brought about by the throwing of the younger strata into sharp synclinal and anticlinal foldings, and the subsequent denudation of the areas from which

• Park, " Geological Reports," 1888-89, pp. 50, 193-199. t Park, on the Collingwood District, " Geologioal Eeports," 1888-89, pp. 50, 193-199.

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