Stream—that is, in the Clutha itself—is to be found a power that will serve to wash away all its auriferous banks, and clear the same to the profit of the miner. The fall of this river, from the lakes to the sea, is about 1,000 feet in 100 to 120 miles, and the area from which it collects its waters above the gorge of the Dunstan is equal to 3,325,000 acres. From these data, we can have a rude or comparative estimate of the power contained in it. Allowing twentyfour inches of fall over the area by averaging the greater fall in the mountains with the lighter fall in the plains, we have 289,674,000,000 cubic feet per annum as the discharge of the Clutha at the above point. This is equal to a discharge of 551,130 cubic feet per minute, but allowing, again, half the rainfall to be absorbed by evaporation, the actual result will be 275,565 cubic feet per minute.

“How to arrive at the object of the inquiry? We have the fall from the lakes to the sea, as above stated, at 1,000 feet, which gives 422,500 nominal horse-power. This may truly be said to be a very valuable property of the province, which always remains to it, and which, if only partially made use of, may be fraught with great importance to the prosperity of our interior population.

“It would not be consistent with the object of this report for me to suggest modes for the economical use of this power; but I may shortly state that I am aware that the mining population have applied it to a limited extent to social purposes. Of all contrivances, however, the simplest, I have no doubt, will prove the most successful, and the merits of the paddle wheel and the marine screw as motive powers will no doubt eventually be much canvassed. I would presumably advocate the latter, on account of its greater hold on the body of the flowing stream, its ready management and applicability in swift or slow currents, and its easy connection with the apparatus for raising water.”

Since the above report was written, of which this is a short extract, though fully alive to the importance of the subject, I have, owing to constant engagements in other works and services, been able only to give an occasional thought in its direction. Since then I have heard of various attempts by miners and others to apply the force of the current of the Clutha to machinery employed in these enterprises, but how far successful they have been I have had no opportunity of learning. Some years ago I inspected two machines, one of which was for the purpose of raising water, and the other for working the gearing of a dredge, and in both cases the principle adopted was that of the paddle wheel, though one was of unusual construction, being set obliquely to the stream. Neither machine had great power, and, having become disused, appear not to have met the expectations of their designers. The paddle wheel, of proper and peculiar form, is no doubt well adapted for driving the machinery of floating mills (flour, bone, saw, etc.) in shallow rivers, where the shallow-

ness of the stream would prevent the screw being applicable, and where there was large floatage capacity, at any rate, required to support the mill and its contents; but the great size, cost, and weight of the paddle form of wheel create a most important objection to its general use in the Clutha, where only the temporary works of gold mining for the most part are engaged in. On the contrary, the great depth of the stream is particularly applicable to the screw, working as it does so much below the surface, and when its smallness and lightness make it so easily handled, and its cheapness and simplicity render it of easy construction and repair.

The floating paddle wheel in a seven mile current requires forty square feet of floatboard to give a power of twelve horses, and of floatboards there require to be eleven in number; while one screw of eight feet diameter would give the same power, and this, instead of requiring to be floated like the paddle wheel high out of the water by sufficiently strong barges or punts, can be immersed and attached not only to barges and punts, but to a buoy, wire rope, boom, bridge pier, piles, or other fixtures suitable to the various situations.

The Otago sluice head, by the Goldfields Regulations, being equal to ninety-five cubic feet of water delivered per minute, machines of the above dimensions will raise one sluice head to an elevation of seventy feet, or seven heads ten feet, and this without intermission day and night.

The advantage of the screw, when made of timber (as I would support) is in its easy construction and repair—this fact should be particularly noted; besides, the screw is the only portion of the apparatus, whether for mills or pumping gear, that need be subject to accidents from floods. Accidents from floods can also be avoided by drawing the screw into the banks till the danger from drifts is over. On the Clutha, with its great body of water, the construction of the screw need not now be scientifically correct, but may be of the rudest description, the fault in form being amply compensated for by the superabundance of power. Thus, the screw may be easily made by a common carpenter and blacksmith—in fact, out of an old gin case and a piece of scantling I would engage to make a very effective two horse-power machine. The contrivance then, I am sanguine in stating, supplies that which is wanted by the sluicing, dredging, pumping, and other enterprises on the banks of the Clutha, viz.,—an inexpensive and simple machine for economising the power of the current. The nature of the contrivance is simple. A model is now on the table for inspection. I will be happy to show it at work in the stream of the Water of Leith, at any time the members of this Society may appoint, when they could judge of its effectiveness themselves.

The model will be seen to be made of wood, in the make-shift fashion much had recourse to on the diggings, the only portion of it executed by skilled labour being the brass force-pump and india-rubber tubing. The screw (or more

properly speaking fan wheel, as the blades in this little example are plain, and not to the helical curve) is fifteen inches in diameter. The blades are set to an angle of twenty degrees to the disc, and in a two-mile current the revolutions are once per second nearly. The pistons of the pump are worked by a crank, and, being single-acting, propel its contents once per second. The diameter of the cylinder is three-quarters of an inch, and stroke of piston 2.7 inches. The quantity of water per stroke is therefore 1.1925 cubic inches. At the above rate of speed, the quantity delivered is therefore 71.55 cubic inches per minute, or 59.5 cubic feet, equal to 368.9 gallons per diem of twenty-four hours. This little model would, therefore, liberally supply the wants of a house of the largest class, and the first cost (not including piping) would not be over four or five pounds sterling.

For town supply, the screw, pump, and gearing would require to be designed for the population; but taking for example one of the largest force-pumps in the works of Messrs. Burt, of this city, I find it to be four inches in diameter, eight inch stroke, single action once per second. This pump, in constant operation, would deliver 3.5 cubic feet per minute, or 5,025 cubic feet, equal to 31,155 gallons for twenty-four hours, which would amply suffice for the supply of a town of 1,000 inhabitants. Had the water supply to be raised 100 feet above the level of the river, such as would be necessary for Balclutha, Alexandra, Clyde, or Cromwell, as one horse-power raises 5.28 cubic feet to that elevation per minute, this power, allowing amply for friction, would suffice for the above service. So, were a screw applied to the pump revolving in a current of seven miles per hour, one of three feet six inches in diameter would do the duty.

The cost of the apparatus complete, delivering water at the top of the bank (not including street pipes, etc.) will of course vary with the nature of the position and relative facilities afforded. Where the river is narrow, the screw and pump would best be held by a wire cable stretched across the current or arm of the river. Where the banks are steep and rocky, a boom secured by stays and guys would be the best mode. Where the river is wide, a small punt, or even a barrel or buoy, might be used, and so forth. In either case the cost would not vary very much, so taking the first by way of example, the following is an approximate estimate:—

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