C—4

2

working one of their present plants. However, as the directors of the different companies are in Auckland, the mine-managers could do nothing but merely express their views on the subject. After meeting the managers we proceeded to Mercury Bay, and next morning went up to Gumtown, thence up the valley of the Waiwawa Eiver, in order to ascertain the practicability of lifting water from that river to get motive-power to generate electricity near Gumtown, so that sufficient power could be transmitted to Kuaotunu, a distance of about twenty miles. The Waiwawa Eiver is the only source from which a sufficient quantity of water can be got, and, in order to get water as a motive-power from this river, it would have to be lifted about 15 chains below the first branch of the river above the Eangihau Junction. I measured the width of the river at the point where the water would require to be lifted, and took the depth at every 10ft., also measuring the surface velocity at different places in the current, and found that there was about 2205 sluice-heads flowing at the time of my visit, and also about 31 siuice-heads in the Eangihau Stream, which would also have to be lifted. The quantity of water at the time of our visit was, however, much more than it would be in summer, and, therefore, a very large deduction would have to be made in making calculations as to the available motive-power during dry weather. From all information we could gather from the residents in the locality, it would appear that there is at least one-third the quantity of water in the river in dry seasons as there was at the time of our visit. If this information could be relied on, then a supply of 84 sluice-heads would be available in dry seasons. According to the barometer levels, taken on going up the valley of the Waiwawa Eiver to the point where the water would require to be lifted, it was 90ft. above the point near Gumtown where the electrical plant would have to be erected; but on getting down to the same place at night the barometer showed a difference of 12ft., the height being only 78ft., and any calculations made are based on the latter height, so that any errors will be on the safe side. The distance that the water would have to be conveyed in an open conduit and flume would be about five miles; the water would have to be lifted out of the south side of the Waiwawa Eiver, and conveyed for the 30 chains in closed boxing, having piles driven at intervals along the line of boxing, and the boxing securely held down so that floods could not lift or damage it. After the first 30 chains the water could be carried in an open conduit having a flume across the Eangihau Stream, and a branch race from that stream to join the main ditch. There would probably be a short tunnel through a rocky bluff, and possibly one through a narrow saddle; but neither of these would be of any great length. Taking, therefore, the length of the water-race as five miles, and allowing sft. of fall per mile, it would leave an available head at the terminating point of 78ft., less 25ft. absorbed in fall, or a hydraulic head of 53ft. Taking, therefore, the quantity of water to be one-third of that at the time of our visit—namely, 5+31 _ Q4 sluice-heads; and 84 sluice-heads with a hydrostatic head of, say, 50ft., that is allowing 3ft. of head to be absorbed in friction in the pipes at the transmitting point of the waterrace, it would give —-— 6 ° *v*—i-— = 4773 theoretical horse-power ; but, as it would not be safe to calculate on a water-motor giving more than 70 per cent, of the theoretical power of the water, this would give an efficiency of 334-horse power for driving the dynamos. But if even a further deduction were made in the quantity of water in dry seasons, and say that there is only one quarter, as at the time of our visit, then this would be 63 sluice-heads, and —° * — Z-zz. = 358 theoretical horse-power, and 70 per cent, of this gives the actual power transmitted by the water to drive the dynamos —namely, 250'5-horse power. Taking, therefore, the loss due to transmission of electrical power by alternating-current dynamos, motors, transformers, and on the line, the former calculation would give about 220-horse power, and the latter 164'5-horse power applied to the crushing-battery. Having shown that there is a water-supply to generate electrical power to drive the present crushing batteries at Kuaotunu, the next question is the cost of the plant, and the expense of working it. Calculating the cost of the plant, provision should be made to use the whole of the available water in the Waiwawa Eiver in dry weather. If it is found necessary, therefore, the open conduit, fluming, and pipes should be large enough to have a carrying capacity of 84 sluice-heads of notwithstanding the fact that 63 sluice-heads would be sufficient for the present requirements; the extra cost in the first instance is not great, and this would then provide more power for future developments on the field. The dimensions of the open conduit to convey 84 sluice-heads of water, constructed on a gradient of 1 in 1056, or sft. to the mile, would be Bft. wide in the bottom, 12ft. wide on the top, and 4ft. deep ; the fluming and boxing would require to be 9ft. wide and 4ft. deep. Of course a conduit and flume of much less dimensions would do if the fall were increased, but the object is to have as large a head as possible at the terminating point of the water-race, and, therefore, the gradient of the ditch and flume require to be kept as low as possible. The banks of the Waiwawa Eiver are tolerably steep all the way up, making it costly to lift the water from both the Waiwawa and Eangihau Streams, also, both these rivers are utilised for floating down kauri-logs in time of floods, so that the boxing alongside the river would require to be very strongly and firmly fixed to prevent the logs from damaging it, when coming down the rivers. These rivers in time of floods rise to a great height, so that covered boxing would have to be carried from the point where the water is lifted to above flood-level, and this would necessitate about 30 chains of boxing at the Waiwawa, and, say, about 20 chains at the Eangihau. It would be impossible to give anything like an accurate estimate of the cost of constructing this water-race without a proper survey being made; but, judging from the nature of the ground, I would estimate the cost of bringing in the water to be from £12,000 to £15,000, including iron pipes at the lower end. Taking, therefore, the estimate of Mr. Fletcher for the electric plant, the expense of erecting an electric plant to work the batteries at Kuaotunu would be as follows; —