C—4

5

As previously mentioned, an efficiency of 70 per cent, has been assumed for the turbines; and, although higher efficiencies are declared by some of the manufacturers, it is doubtful if, in practice, any of them would be prepared to guarantee more than 70 per cent. An efficiency of 90 per cent, has been allowed in the foregoing calculations for the electric generators and motors, and 95 per cent, for the transformers. These efficiencies are below those claimed by the manufacturers, but may be relied upon if properly-designed apparatus suitable for the work is employed. Eecent careful and elaborate tests made in England of transformers of various makers gave efficiencies as high as 96-9 per cent., while all the best gave 95 per cent, and over. For driving the electric generators it would be desirable to use two turbines and horizontal shafts, each turbine being coupled direct to two electric generators, one at each end of its shaft. Such an arrangement, by avoiding the use of driving-belts or intermediate gearing, would be very compact and serviceable, economising power and saving wear and tear, also affording facilities for overhauls or repairs of turbines when such are necessary. Alternate current generators and motors possess considerable advantages with regard to the comparative ease with which repairs can be effected. The generating-coils are practically the only parts liable to damage ; but these are so subdivided, interchangeable, and easy of access, in welldesigned machines, that a workman of ordinary intelligence could replace an injured coil in a very short space of time, spare coils for the purpose being provided. In an installation of this nature, there is hardly any necessity to provide duplicate plant. The chances of a serious break-down are remote, while a temporary stoppage of a few minutes would not cause the inconvenience that might occur if the electricity was being used for lighting purposes. Having the plant in two units, by sections, further reduces the possibility of a total stoppage, so that hardly anything short of a collapse of the water-race or break-down of the power-line would produce such a result. If it was found, after the plant was installed, that the large amount of water (84 sluice-heads) could be depended upon, and that there was demand for such power, another turbine and electric generator could be erected, provision being made, in the first instance, in the design and arrangement of the plant, for possible future extensions. There would not be any particular advantage in commencing operations with less generating plant than that necessary for the minimum water-supply (63 sluiceheads) ; as, although there would be a saving in the first outlay in plant, the cost of water-race and power-line would be the same, and there wpuld be no reduction in the cost of attendance and general working-expenses. The estimate of cost of installation and annual working expenses here given is for the power delivered at Kuaotunu, and includes cost of electric motors and distributing apparatus. No allowance has been made for fixing motors, or adapting existing intermediate gearing at the various battery-houses, nor for connecting motors to distributing-station at Kuaotunu. This latter item will depend on the distance of the various companies' works from the station, and to some extent upon the amount of power they may require. The distance, in most cases, would not exceed one mile, but, as the companies would have to pay for the power lost in their connecting-wires, it would not be advisable to attempt to economise too much in the first outlay. At an average cost, about £70 to £80 per mile for poles, insulators, wires, and erecting, may be assumed. Fixing motors would cost very little, as they are compact and self-contained. Alterations to intermediate shafting to suit speed of motor, assuming that a steam-engine has been previously used, is the only other expense of installation. This would have to be considered for e_|ch particular case, but, probably, the cost of an extra pulley or two would meet requirements in most instances. The cost of waterrace has, upon Mr. Gordon's suggestion, been estimated at £1,000 per mile, including cost of fluming at intake. This price is, no doubt, on the safe side, but it is impossible to form a very correct estimate until the ground has been properly surveyed, and the route definitely fixed. With regard to labour, it will be noticed that provision has been made for four men, three of whom would be at the generating end, and one at Kuaotunu. With everything in good order there is hardly anything for the men to do at the generator-house beyond occasionally oiling the machinery and seeng that everything is working right. There are few moving parts in a turbine, or electricgenerator, and a turbine and generator would be coupled one to the other. The absence of belts, intermediate shafting, or gearing leaves very little to get out of order. Two men could do all that is required in the twenty-four hours, with two or three shifts, whichever might suit them best. The third man's duty would be to look after the water-race, and any other odd jobs that might arise. As the generating-station would be in a comparatively civilised locality—that is to say, there is a decent hotel and general store at Gumtown—it has not been considered necessary to provide house-room for the men, as they would, no doubt, make their own arrangements. It would be necessary to have a man stationed at Kuaotunu to look after the transformers and electric motors. One of the battery hands at each of the works, where the power was being used, could give such attention as the motor requires, during his shift, without interfering greatly with his ordinary duties; while the man, whose duty it was to see that the various motors were kept in good order, would always be within call, in case of any trouble arising, to set things aright again. Telephonic communications would exist between the various works using the power, and also between Kuaotunu and the generating-station. The items " Interest " and " Depreciation " speak for themselves, and require little comment. In an installation of this nature 5 per cent, is a very fair sum to allow for depreciation of the electrical and water plant. With regard to the water-race, there is very little to depreciate beyond a few chains of fluming that would be required. As provision has been made for a man to look after the race, and make such repairs as may be necessary from time to time, 2J per cent, is a fair allowance for material for making such repairs. It will be noted that the cost for break horse-power, delivered at Kuaotunu, works out at £13 18s. 4-J-d. per annum for 165-horse power, and £11 9s. 3'6d. for 219-horse power. This might have been expected; for, although the cost of plant is increased to provide the larger amount of power, the general and working charges do not increase in proportion. It is difficult to make comparisons between the cost here given per electrical break horse-power, if it may be so called, and an imaginary steam-