One of the greatest objections to gas as an indoor illuminant is the fact that not only does it burn a large amount of the oxygen of the air, but it also gives off during combustion carbonic acid gas and other poisonous vapors, besides a great amount of heat, thus vitiating the atmosphere. In public buildings where there is much gas burnt and little ventilation, this is seen to advantage, the air becoming in a short space of time hot and unwholesome. Now in the case of the incandescent electric light, this is altogether altered, the incandescent filament which produces the light, although in itself enormously hot, is too small in point of size to radiate much heat, and the fact of its being hermetically enclosed in a glass globe, which is impervious to the atmosphere, entirely prevents the escape of any noxious gases. The same circumstance prevents there being any consumption of oxygen.
These facts make the electric light far more wholesome than gas for the illumination of music-halls, churches, or other places of concourse. In a recent trial in the Town Hall at Birmingham, the employment of gas raised the temperature of the atmosphere thirty-eight degrees in three hours, while the building was equally well lighted with electricity for seven hours with a rise in temperature of only two degrees. Thus, after a period of lighting by electricity 2.33 times as long as by gas, the temperature at the ceiling was increased by only 1-19th of the amount due to gas.
Another great advantage consequent to the employment of incandescent lighting, is the greater immunity from accidental fire; for as the carbon filament is instantly entirely consumed, the moment the glass envelope is broken it is impossible for the lamp to ignite anything in its vicinity however inflammable. The experiment has been tried of breaking a lighted incandescent lamp in a vessel containing gunpowder, with perfect safety. As these lamps may be placed in any position, they lend themselves very readily to ornamental and decorative purposes. At the recent electrical exhibition at the Crystal Palace a very beautiful chandelier of Edison lamps was shown, in which the lamps, which were of very small size, formed the petals of finely worked glass and brass flowers. This chandelier had a really magnificent effect when lighted.
These and other facts too numerous to mention, demonstrate that electricity, when properly applied, will be a far more elegant, safe, and wholesome agent for illuminating purposes, than coal-gas as now employed. But in order to have the full benefits of its use, a system is required by which the electric current shall be produced and conveyed to the lamps.
Not only has Mr. Edison invented an incandescent lamp, but he has also identified his name with a very complete system for producing the light on a large scale to suit both domestic and commercial requirements. In the first place he has invented a peculiar form of dynamo-machine, which when driven at great speed by powerful steam or water engines, produces the electricity in great quantity at some central station. From this centre the current is conveyed by copper wires laid under the streets or over the roofs of the houses, these conductors being tapped of their electric fluid by smaller wires which convey the electricity into the houses, in a way similar to that in which gas is conveyed by small pipes from the larger street mains. In each house is an electric meter, a special invention of Mr. Edison’s, which measures the quantity of electricity which passes through it. This meter is very ingenious, and therefore the principle on which it is based may be described. If a current of electricity be passed through a solution of sulphate of copper, contained in a copper jar, the sulphate solution is decomposed and metallic copper is deposited on the inside of the jar. Now it has been proved by experiment, that the amount of copper deposited is always directly proportional to the strength and duration of the electric current. Mr. Edison’s meter consists of such an arrangement, and he finds that by weighing the copper jar, so as to determine exactly what it has gained in weight through the metallic deposition of the solution it contains, he can accurately calculate in units the amount of electricity that has passed through the meter. By means of this beautiful discovery electricity can be supplied and paid for in a manner very similar to that employed in the case of gas at the present time.
Within the building to be illuminated, the electric fluid reaches the lamps along small copper wires, about the thickness of ordinary bell wire, which are covered with a coating of gutta percha to prevent the escape of the electricity, which might cause sparks or even fire, or in any case seriously injure any one who might come in contact with the bare metal, by giving him a very violent if not fatal electric shock. The lamps themselves may be fixed to ordinary gas brackets. Mr. Edison has designed some special ones, and the light can be turned on and off, by means of a tap or button, with as great or even still greater facility than gas.
Mr. Edison has recently established a central station in New York, from which he proposes to light the houses included in an area of a wide radius from the center. In part of this area the installation of the lamps and wires is now complete, and the light is giving every satisfaction, the cost being considerably below that of gas, which in the United States is very expensive. It must be remembered that electric lighting is comparatively a new science, and not yet fully understood. There is very little doubt that, by practice, it will before long approach more nearly to perfection, and sooner or later entirely supersede gas, the arc form of lamp being employed for the illumination of streets and large areas, while the incandescent pattern meets domestic requirements.—Good Words.
