On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
The apparatus exhibited by Messrs. Wells&Co., of Bhoreditch, for the production of electric light by the Jablochkoff process, is shown in the engraving, for which we are indebted to the London Graphic. It consists of a Gramme machine, a section of which is given to show the arrangement of magnets around a central axis. This rotates about 1,100 times per minute, and is driven by any ordinary engine. The Jablochkoff candle consists of two sticks of moulded carbon, embedded in a mass of composition to give them solidity, and are separated by a column of plaster of Paris, whichacts as an insulator. The two carbons are connected at top by means of a thin stick of carbon one millimeter in diameter. The entire candle is held in a strong metal clip. Four of these are contained in a lamp, and are burnt in succession, an automatic arrangement shifting the current as each one is burnt out. Messrs. Wells exhibited three of these lamps inside and one outside of their large show rooms, the illumination of which was perfect, showing colors distinctly, and, being diffused, did not cast heavy shadows. They afterwards burnt six candles on one stand, simultaneously producing a brilliant light and solid shadows. As to the light itself, there is but little difference, and that only to be noted by experts, between it and the light produced by the systems that have already been adopted in London. It is of a very powerful character, and it extends Its illuminating influence for a considerable distance without much apparent diminution of strength. electric candle consumes per hour 77 grains of crayon, composed simply of coke and plaster; the ton of best coke costs 9.00, and the pound of plaster 3 cents. Taking these figures as a basis, we find that the consumption of my candle, representing 100 jets of gas, costs 0'0055 cent per hour, which gives a figure almost impossible to formulate. Multiplying by 1,000, we may say that an electric light replacing 10,000 jets of gas costs 5 cents, while these 10,000 jets represent an expense of 84 cents per hour. No one could prove these figures inaccurate, and yet I should never dare to represent them as realizable in practice. As to the cost of the electric light, I shall only say this--wherever it has been employed there has been a very notable economy. In the Louvre, for example, where this light has been in use for a year, the proprietors of the magasins have proved a saving of 30 per cent, and with more light than with gas. I conclude by saying that progress in the cheapness of the light is clearly indicated. The electric candle, which is manufactured at this moment at the rate of from 3,000 to 5,000 per day, and in consumption costs 10 cents per hour, must necessarily become cheaper when we manufacture 50,000 per day; but to announce the future eventual result as an accomplished fact is to mislead the public. - < i > --- Recent Military Balloon Experiments. The military balloon experiments at Woolwich have been so far successful that lately an aeronaut was lifted some 700 feet, to a height, therefore, sufficient for reconnoitering purposes. There is nothing of novelty in this, as a matter now passed through the tube, and hydrogen issues forth, the oxygen from the decomposed steam going to form ferrous oxide. So completely do the iron turnings do their work under these circumstances, that not only is the surface of the metal acted upon, but it is oxidized well nigh throughout. Naturally enough, the hydrogen comes away with a good deal of vapor, and, if pure gas is desired, some desiccating arrangement will have to be employed; but so far Captain Templar has used none. His balloon, which is of lawn, dressed with boiled oil and glue, will contain about 10,000 cubic feet, but last week not more than 9,00 feet of hydrogen was introduced. The gas was generated from the tube at the rate of something like 1,000 cubic feet per hour, and there can be little doubt that, during the long period of filling, a large quantity of the vapor that was mixed with the hydrogen condensed and ran out of the balloon in the form of water. Pure hydrogen should have a lifting power of 70 lbs. per 1,000 feet, or perhaps a little more, but it is hardly likely that gas produced in a rough and ready fashion in the field will possess this degree of buoyancy. Still Captain Templar was successful in lifting balloon, aeronaut, ballast, and 700 feet of rope--for the ascent was a captive one--by means of 9,000 cubic feet of hydrogen, prepared in the way we have mentioned. Another point is worthy of note in connection with the experiment. The fabric of the balloon kept the hydrogen imprisoned for a much longer period than had been anticipated. A dozen hours scarcely impaired the buoyancy of met cfccwi 7ejjiwff,rfiectf. of gramme THE ELECTRIC LIGHT.--SKETCH OF- THE APPARATUS. M. Jablochkoff, the inventor of this form of the electric light, writing in reply to the question as to what distance from the source of electricity a luminous center may be produced, says that the distance may be as great as is wished, only it is necessary to employ a conductor of very great diameter in order not to increase the total resistance of the circuit. In reference to Mr. Edison's claim to have solved the question of the divisibility of the light, M. Jablochkoff writes that he long ago realized its divisibility, as is proved by communications from him to the Academy of Science and the French Physical Society, in December, 1877, and February, 1878. It has, moreover, he states, been shown in public at the Sorbonne, and has been in use at the Exhibition since the 1st of May. M. Jablochkoff says: "In view of this fact, it may not be inadvisable to say a few words on the calculations which have been made as to the cost of the light. These calculations are of two orders. The opponents of the electric light represent it as costing very dear; its partisans, and, above all, its propagators, on the contrary, give figures which we may not, perhaps, call inexact, but which, nevertheless, are only theoretical figures, and, consequently, little capable of being justified by practice. To better understand my idea, I shall suppose the following calculations for my candle. The of aerial navigation, although it is the first instance, we believe, of any one in this country being raised from the earth by the agency of pure hydrogen, but it is, nevertheless, something to have achieved in the circumstances under which Captain Templar has been working. Everybody knows that hydrogen is gifted with extraordinary lifting power, just as every chemist is aware that the gas may be produced in the way Captain Templar produced it, namely, by passing a jet of steam over iron turnings. But the problem under solution was not to send up a hydrogen balloon so much as to discover whether the thing could be done in a haphazard fashion, and with such simple means as an army in the field would be provided with. It is one thing to make hydrogen in the laboratory, and another to make a sufficient supply of it just whenever the commander of an army may order a balloon reconnoissance to be made. Captain Templar has practically proved that this can be done. He requires a supply of steam, an improvised furnace of some sort, and a tube filled with iron turnings; given these, he can provide hydrogen sufficient to lift a scout high into the air. The tube at present employed by Captain Templar is six or eight inches in diameter, and some half dozen feet long; it is filled loosely with iron turnings and placed in a furnace where it becomes red hot. Steam is the balloon, and by adding yet another waterproof coating it is anticipated that the balloon will remain inflated for four-and-twenty hours. The next step will be to discover how far it is possible to compress hydrogen so manufactured into cylinders for conveyance in transport wagons, so that a supply of hydrogen may be at hand whenever an ascent is determined upon in the field. Captain Templar is sanguine of compressing the gas to a fourth of its volume, and thus decreasing its bulk considerably, when the balloon train is on the march. How far this is practicable experiment only can prove.--Nature. Spontaneous Combustion. According to the Boston Journal o Commerce, at the semiannual meeting of the New England Cotton Manufacturers' Association, in Boston, Professor Ordway made a report on certain chemical properties of commercial oil, and incidentally discussed spontaneous. combustion. Experiments had been attempted to ascertain the facts concerning spontaneous combustion, which is oxidation of oil when spread out over a large surface. It was found that in time all oil, whether animal or vegetable, took fire. One of the most important things to be ascertained in the experiments was the correctness of the opinion put forward as a result 1878 SCIENTIFIC AMERICAN, INC. November 23, 1878.] Jtxtutxtxt jmttxau. 327 of recent experiments in Europe, that animal or vegetable oil when mixed with a mineral oil would undergo spontaneous combustion. It was found that cottonseed oil would take fire even when mixed with 25 per cent of petroleum oil. But it was ascertained beyond a doubt that even 10 per cent of mineral oil mixed with an animal or vegetable oil went far to prevent combustion. Professor Ordway described some experiments in other directions, but explained that they would have to be continued before definite deductions could be made. In connection with the tests of the flashing point, experiments had been made with ten specimens of kerosene oil bought at different stores in Boston. The flashing point should be at 130 Fahrenheit. Downer's kerosene was found to be ;ood at 134, but the other specimens flashed respectively at 84,80, 81, 117, 79, 73, 125, 79, 80, 84 degrees. The professor was of the opinion that it was lime tor somebody to iook after the kerosene oil sold and used in Boston, when out of ten specimens bought at random only one was fit to use with safety. He remarked the fact that oils bought under the same name, from the same manufacturer and at the same price, differed very much in quality. Another remarkable circumstance was that some oils which flashed at a low point were high priced, and vicevice versa. Closing, the professor recommended that manufacturers of oil should be aroused to a greater sense of their responsibility.
