The Daily Telegraph. MONDAY, FEBRUARY 19, 1883.

Daily Telegraph (Napier), Issue 3621, 19 February 1883, Page 2

The Daily Telegraph. MONDAY, FEBRUARY 19, 1883.

"Lighting Country Towns by Electricity or Gas " is the subject of a small pamphlet by MrR, li. Shakcspear, C.E., of Melbourne. The object of the work is to show that, while lighting by electricity has proved successful when required on a large scale, the system is by no means economical when applied to places where a moderate amount of light is only wanted. Mr Shakcspear points out that in well-lighted streets a larger amount of illumination is obtainable from the use of electric arc lights at a less cost than is possible with gas. In small colonial towns, however, where the streets are but inefficiently lighted, the increased light from elecrieity is obtained only at a largely increased cost. Dr. Siemens is reported to have stated in his inaugural address as chairman of the Society of Arts that "electric lighting by incandescence, when carried out on a large scale, is decidedly cheaper than gas in annual cost, but the cost of the plant to supply gas on a large scale would be less than one-half than that required to supply an equivalent light by elecrieity." In the same address Dr. Siemens also expressed the opinion that electric lighting must win the day as the light of luxury, but gas would" at the same time rind an ever increasing application for the more humble purposes of diffusing light. For lighting- the streets of a town with electricity, arc lights are used, which are either of very considerable power and exhibited at considerable elevations above tho streets, so as to illuminate large areas from one lijjfht or set of lights, or the lamps are placed at moderate heights of from fourteen to twenty feet above the street and at short distances of about five chains apart. Tho objection to the former method is that tho shadows, where the light is intercepted, are very dense, and a large waste of light and consequently of power occurs into space above the level at which light is needed by the passengers in the street. Under the second system each arc light requires the expenditure of about one indicated engine horse-power, and a loss amounting to as much as 25 per cent takes place when the lights are scattered as far as about two miles from tho engine-power. Thus, to light a mile of street Avould require sixteen lamps with a motive power of nineteen indicated engine horse-power. The system of inside or house lighting is by means of incandescent lamps, which arc small glass globes, of the size of an egg, enclosing the incandescent carbon filament which gives oft' the light. Each incandescent lamp has practically about the same illuminating power as an ordinary gas jet, if the gas be of good quality, so that one incandescent lamp must in practice be substituted for each previous gas-burner. And thus, if a town be estimated to require a certain number of gas-burners, an equivalent number of incandescent lights must be provided, and in the ordinary town at least, an equivalent number of arc lights to the existing number of gas or oil lamps, since the latter are rarely placed so close _ as five chains apart. One indicated engine horse power will suffice for only from seven to nine incandescent lamps, and, as has been previously stated, one horse power for each arc light: and thus, upon tho basis of these figures, a comparison may be arrived at in the case of any town, bet-ivesa the

cost of the plant required for gas or electric lighting, and also of the relative annual cost of production. One great advantage that gas possesses over electric lighting is that with the former no extra plant is required to meet an extraordinary demand. With gas works it is necessary only to manufacture per day such quantity of gas as will meet the ordinary daily average demand, for any excess in requirements would bo met by the gas previously in the holder, or, in case of an unusual demand, such as on the first occasion of lighting the town, the gas can bo delivered also direct from the retorts as rapidly as it ismanufactured ; or, to extend the case still further, the retorts may be charged more frequently and the charges drawn before the distillation of the whole is complete. Thus the gas plant is capable, without additional cost, of meeting very largely increased demands, both in the hourly supply of gas and in the number of hours during which such supply is maintained. This capacity of extension in the supply of electricity is only obtainable by duplicating the plant, whilst if duplicated an extension of the number of hours of supply, even to meet the case of very few lights, would necessitate the working of one of the engines for the .same period, during which time it could be only worked at a loss. Again, assuming it were required that a gas plant should be capable of lighting 1000 lights simultaneously—although under ordinary circumstances but 600 would be thus lit—the sras manufacturing power need not be equivalent to the 1000"lights, but only somewhat in advance of the GOO ; for the store in the gas-holder, together with pressing the manufacture, would meet tho occasion; but in the case of electric plant, the manufacturing - power must be equal to that for the 1000 lights, all lit at one time, since no efficient and economical method of storing in large quantities has yet beeen devised, which would be applicable with safety in such instances.