Acetylene, the Principles of Its Generation and Use | Page 7

choice of electric lighting. But in the cases where there is no public gas-supply, and current must be generated from coal or coke or oil consumed on the spot, the cost of the skilled labour required to look after either a boiler, steam-engine and dynamo, or a power gas-plant and gas-engine or oil- engine and dynamo, will be so heavy that unless the capacity of the installation is very great, acetylene will almost certainly prove a cheaper and more convenient method of obtaining light. The attention required by an acetylene installation, such as a country house of upwards of thirty rooms would want, is limited to one or two hours' labour per diem at any convenient time during daylight. Moreover, the attendant need not be highly paid, as he will not have required an engineman's training, as will the attendant on an electric lighting plant. The latter, too, must be present throughout the hours when light is wanted unless a heavy expenditure has been incurred on accumulators. Furthermore, the capital outlay on generating plant will be very much less for acetylene than for electric lighting. General considerations such as these lead to the conclusion that in almost all country districts in this country a house or institution could be lighted more cheaply by means of acetylene than by electricity. In the tabular statement of comparative costs of different modes of lighting, electric lighting has been included only on the basis of a fixed cost per unit, as owing to the very varied cost of generating current by small installations in different parts of the country it would be futile to attempt to give the cost of electric lighting on any other basis, such as the prime cost of coal or coke in a particular district. Where current is supplied by a public electricity- supply undertaking, the cost per unit is known, and the comparative costs of electric light and acetylene can be arrived at with tolerable precision. It has not been thought necessary to include in the tabular statement electric arc-lamps, as they are only suitable for the lighting of large spaces, where the steadiness and uniformity of the illumination are of secondary importance. Under such conditions, it may be stated parenthetically, the electric arc-light is much less costly than acetylene lighting would be, but it is now in many places being superseded by high-pressure gas or oil incandescent lights, which are steady and generally more economical than the arc light.
The illuminant which acetylene is best fitted to supersede on the score of convenience, cleanliness, and hygienic advantages is oil. By oil is meant, in this connection, the ordinary burning petroleum, kerosene, or paraffin oil, obtained by distilling and refining various natural oils and shales, found in many countries, of which the United States (principally Pennsylvania), Russia (the Caucasus chiefly), and Scotland are practically the only ones which supply considerable quantities for use in Great Britain. Attempts are often made to claim superiority for particular grades of these oils, but it may be at once stated that so for as actual yield of light is concerned, the same weight of any of the commercial oils will give practically the same result. Hence in the comparative statement of the cost of different methods of lighting, oil will be taken at the cheapest rate at which it could ordinarily be obtained, including delivery charges, at a country house, when bought by the barrel. This rate at the present time is about ninepence per gallon. A higher price may be paid for grades of mineral oil reputed to be safer or to give a "brighter" or "clearer" light; but as the quantity of light depends mainly upon the care and attention bestowed on the burner and glass fittings of the lamp, and partly upon the employment of a suitable wick, while the safety of each lamp depends at least as much upon the design of that lamp, and the accuracy with which the wick fits the burner tube, as upon the temperature at which the oil "flashes," the extra expense involved in burning fancy-priced oils will not be considered here.
The efficiency (_i.e._, the light yielded per pint or other unit volume consumed) of oil-lamps varies greatly, and, speaking broadly, increases with the power of the lamp. But as large or high-power lamps are not needed throughout a house, it is fairer to assume that the light obtainable from oil in ordinary household use is the mean of that afforded by large and that afforded by small lamps. A large oil-lamp as commonly used in country houses will give a light of about 20 candle- power, while a convenient small lamp will give a light of not more than about 5 candle-power. The large lamp will burn about 55 hours for every gallon of