Open main menu

Page:Popular Science Monthly Volume 18.djvu/439

This page has been validated.

bow. The carbon, which is made from paper or wood, is not placed in a vacuum, but in a rarefied atmosphere of gasoline, the idea involved being that, as the strip wears away under the action of the current, it will be continually renewed by the free carbon of the dissociated hydrocarbon vapor. This deposited carbon forms a hard, compact layer which seems to greatly increase the durability of the strip, and also the amount of light which it will yield under a given current. None, it is stated, have broken, even when forced much beyond the incandescence they are intended to bear, and, owing to the compensating action of the gasoline, it is anticipated that the lamps will be permanent. The platinum wires supporting the carbon strip are not fused into the glass of the bulb, as has been the case in previous incandescent lamps, but are surrounded by a slightly elastic cement, which it is averred preserves a good joint. The light given by the lamp is but slightly yellow, is quite pleasing to the eye, and is fairly steady. It has, however, a perceptible vibration, different from the irregular flicker of gas, but more painful, and which it seems impossible to eliminate, as it is due to the necessary variations of the engine-speed. As to cost, the inventor, Mr. H. S. Maxim, claims that he is able to produce ten lights of twenty candles each per horse-power. Professor Henry Morton, of the Stevens Institute, in a paper read before the American Academy of Science, at its recent meeting, stated that, experimenting with one of these lamps, he found that, when it was giving a light of forty candles, the expenditure for power was at the rate of 240 candles per horse-power. A twelve-candle light was at the rate of 136 candles, and, at 49 candles, was at the rate of 426 candles for the same power; while, when the lamp was forced to 98 candles, the expenditure was at the rate of 607 candles per horse-power. He also bore testimony to the value of the gasoline vapor in building up the carbon strip. It is doubtful, however, if the gasoline will prove in practice as free from disadvantage as expected. It will probably deposit in the form of a film on the glass, that may in time so obscure the light that a new lamp will be necessary. Such a deposit seems to have already taken place in some of the lamps at present on exhibition. The regulating device is quite simple in construction and certain in action. Its general mode of operation is as follows: The field magnets of the machine supplying the currents to the lamps are excited by another machine. The current furnished by this latter is varied in accordance with the number of lamps in circuit, by shifting its commutator brushes to and from the position in which they take off a maximum and minimum current. This shifting of the brushes is done by means of simple mechanism, actuated by an electromagnet placed in the lamp-circuit, and therefore subject to the same conditions as the lights. Numerous trials have shown that this regulator is entirely reliable, and the adjustment of the current is so delicate that no observable difference has been detected in the light of a lamp whether one or sixty were in circuit.


The German Anthropological Society.—The eleventh meeting of the German Anthropological Society was held at Berlin, August 5th to 12th. The greater proportion of the papers read during the sessions related to relics discovered in Germany and the neighboring countries, most of which were newly found, or newly reported upon. Among the subjects of these papers were prehistoric earthworks and fortifications in Schleswig-Holstein; a Frankish burial-ground near Worms, in which burials in rows and in several courses of bodies were notable features, and where dogs and horses were found buried with the men, together with vessels of clay and glass of extraordinary size and beauty, and a unique bronze cup adorned with Christian emblems; the Frankish castle of Schlosseck in the Isenach Valley near Dürkheim, hitherto wholly unknown; a report by Professor Virchow upon the results of statistical researches into the color of the skin, hair, and eyes, illustrated by maps and tables; prehistoric charts of Germany by Professor O. Fraas; the German Runes, by Dr. Henning, of the University of Berlin. Dr. A. Bastian, who had returned from a journey of more than two years, undertaken for the study of facts relating to anthropology, spoke of the immensity of the task of perfecting the science, which he realized more completely than