SOLAR MOTOR, a mechanism for secttr ing motive power from the sun. For many years the attention of inventors has been di rected to the question of utilizing the direct rays of the sun as a substitute for coal, wood or other fuel; large burning-glasses or reflectors being the general form of the various machines. A so-called oburning made in France by Villette, was four feet in diameter, and pro duced so intense a heat that, according to the report, it melted cast iron in 16 seconds, prob ably an exaggeration. It was for a long time difficult to build a concave mirror of very large size, but this was finally overcome by having the surface of the concave mirror covered with small pieces of glass, or mirrors, each of which is so placed that the light or reflection from each side is thrown upon the same spot, the sum total, or the amount of heat centralized, being equivalent to the amount reflected by each glass, mutiplied by the number of mirrors. In Europe the early solar glasses were generally of two kinds; that is, the heat was concentrated in two ways — by reflection from polished con cave mirrors and by refraction through a con vex lens. The earliest use, centuries ago, of such a contrivance was theoretically to dazzle or blind an enemy, metal discs being employed; but nearly all such devices failed to be of any i5ractical value. Sir William Herschel experi mented with the sun's heat in Africa; and Captain Ericsson made a number of studies in this direction and exhibited a solar motor in New York in 1884.
Within recent years a successful sun motor has been built at South Pasadena, Cal., and here is an automatic engine run by the heat of the sun. In appearance the motor resembles a huge dish of glass, with a central aperture, and at a distance might be taken for a windmill; but the dish is a reflector 33 feet in diameter. The
inner surface is made up of 1,788 small mir rors, arranged so that they concentrate the sun upon the central or focal point. Here is sus pended the boiler, which is of tubular form and 13 feet long, holding 100 gallons of water, leaving eight cubic feet for steam. The motor is attractive in appearance; built lightly, sup ported by seeming delicate shafts, though in reality strong enough to resist a wind pressure of 100 miles an hour. The reflector must face the sun exactly, and as heavy as it is, weighing tons, it can be easily moved. It stands, after the fashion of the telescope, upon an equatorial mounting, the axis being north and south; the reflector follows the sun, regulated by a cock, the work being automatic, as, in fact, is every thing about it. The true focus is shown by an indicator, and in about an hour after it is lid justed in bright sunlight the steam gauge will register 150 pounds. The steam is carried from the suspended boiler to the engine in a flexible tube and returns again from the condenser to the boiler in the form of water, so that the boiler is kept automatically full. The engine is oiled automatically, and when the dish is once turned, facing the sun, it runs all day ai independent of an engineer as does a windmill, developing about 12 horse power. While the motor is most interesting to engineers, it has not demonstrated the practicability of the sys tem in competition with the ordinary steam engine or electric power brought from a distance.