way. The most economical size of cable depends on what we can afford to lose. No. 6 shows the increased cost if the power is taken off by small motors instead of one large one. Nos. 7, 8, and 9 are long-distance schemes, with a higher E.M.F. No. 8 is probably the best arrangement, as to reduce the loss to 4 horse-power it is necessary to spend £1000 more on the line-as in No. 7. No. 9 is as far the other way, as what we save in the line causes an excessive loss in power, and the generator costs more, having to be more powerful to overcome the extra resistance. No. 8 is made up as follows: Generator and motor, foundations, &c., £820 55 815 90 £1800 No. 13 shows that for less than £3000, 50 horse-power can be transmitted 20 miles; the cost of copper conductor is nearly half the total, and if the percentage of loss were increased, a considerable saving in cost could be effected. Nos. 14 and 15. When the power is over 300 horse-power, it is advisable to have two motors; this reduces the risk, and the cost is much the same as having one large machine. From what we have shown, it is clear that electricity is the only means of transmitting power economically over considerable distances. The town of Carlow in Ireland is lighted with electricity, and is an interesting example of long-distance transmission. The water-power is at Milford, on the river Barrow, 53 miles from the town. There are two turbines of 50 horse-power each, with a fall of 7 feet; these drive an alternating current dynamo generating current at 2300 volts, this is conveyed by underground cables. The high-pressure mains are led into a switchhouse at Carlow, and divide into three circuits carried on posts overhead. There is also a complete network of low tension mains extending through 5 miles of streets. Transformers are fixed on the posts themselves, and feed into the low-tension network. This arrangement is simple and effective, and the cheapest that could be devised. The commercial success of this enterprise is of considerable public importance, as Carlow is not a wealthy town, and may be taken as a fair average representative of many hundreds of similar towns. The whole of the water-power arrangements, turbines, &c., were designed and constructed by the author. After hearing so much about what is being done abroad, it is pleasant to report that some progress has been made in various parts of Scotland. In the county of Inverness there has been erected during the past two years fourteen electric light installations, with water as the motive power. One of these, carried out by the author at Loch Rosque Lodge, Ross-shire, possesses some interest from the fact that a fall of 650 feet is applied to the turbine, and as far as is known, this is the highest fall applied to power purposes in the kingdom. The water is taken from a mountain stream, and a storage of 20,000 cubic feet provided by a dam formed in a natural hollow. The water is conveyed partly in an open cutting and partly by fire-clay pipes for half a mile to a settling tank 650 feet above the turbine, to which it is carried by riveted steel pipes 600 yards in length; 35 horse-power is obtained. The total cost of the hydraulic part of the apparatus was £700. Allowing 5 per cent. interest, and 5 per cent. depreciation, the cost is only £2 per horse-power per annum. The cost for attendance is trifling. Another water-power electric light scheme has been carried out by the author at Duntreath Castle, Stirlingshire. Here a fall of 300 feet is obtained, and with a high-pressure turbine produces 25 horse-power. A small dam to store 40,000 cubic feet is provided. The total cost is about £800, making the annual cost £2 to £3 per horse-power per annum. The only electric railway in Scotland is a private line, 11 miles long, on the Carstairs estate. It extends from Carstairs House to Carstairs Junction on the Caledonian Railway system. The gauge of the line is 30 inches. The source of power is a waterfall 3 miles distant. The turbine, which has a working head of 40 feet, drives a series dynamo giving 40 volts 40 ampères, or 20 horse-power. Besides working the railway, this turbine and dynamo are used to light the house, saw wood, and drive farm machinery. There are several small towns in Scotland at the present time contemplating the introduction of electric lighting by water-power, and in a country so highly favoured by nature as ours for such a purpose, it will be strange if native enterprise is wanting to carry these schemes to a successful issue. On Improved Turbines for the Utilisation of Water for Power. By JOHN RITCHIE, C.E., Edinburgh. (With Plates.)* In the first portion of the communication on the "Utilisation of Water for Power" made to this Society, the subject was treated generally. The sources of power and examples of the successful application of such in various parts of the world were given. In this paper I shall describe some of the means through which the power of water is applied. In order to transform the weight of water into energy, it is necessary that the water should fall through a certain space, and to get this fall is the first object of the engineer. In streams, this is generally obtained by the construction of a weir, the water being carried to the motor by an open cutting, or channel, or by a pipe. For falls up to 10 feet it is usual to have an open cutting or an earthenware pipe, and in falls over 10 or 12 feet to use an iron pipe. As the use of the ordinary vertical water-wheel is, except for very special purposes, all but superseded by some form of turbine, I will confine my remarks to the latter machine. Where the fall is limited, the proper construction of the inlet channel, or head-race, is of great importance, if full advantage is to be taken of it. The sectional area should be * Read before the Society, 10th April 1893. MR JOHN RITCHIE ON TURBINES. Trans. Roy. Scot. Soc. Arts, Vol. XIII. Fig. A.-PRESSURE TURBINE in open Iron Flume. SUITABLE FOR A LOW FALL. |