542 



SCIENCE. 



ELECTRIC LIGHTER OF M. DESRUELLES. 



This is a small apparatus, simple and practical, which 

 will certainly be very highly appreciated by smokers and, 

 in g' neral, by all persons who are often in need of fire 

 or light. It is one of the most direct applications of the 

 drying of piles of all the systems by the process of M. 

 Desruelles. This process consists of introducing in the 

 piles, in the place of liquid, a kind of amianthus sponge 

 that is afterwards filled with acid or some suitable solu- 

 tion. We thus gain by having a pile dry to some degree, 

 which can be removed, displaced, or reversed without the 

 liquid pouring out ; this has its advantage for movable 

 machines, such as portable lamps, piles for bells on board 

 of ships, railroads, etc. The introduction of this inert 

 substance diminishes the volume of the liquid ; without 

 saying that the electromotive force of the pile is not at 

 all affected, its interior resistance is increased. This is 

 of no importance in the case which we are now consid- 

 ing. The lamp consists of a small round box of wood, 

 in which the pile is placed ; over this box is placed a 

 small lamp with oil ; a platinum spiral in juxtaposition to 

 the wick serves to produce the light. 



The pile is an element to the bichromate of potash, 

 in which the liquid is replaced by a kind of amianthus sat- 

 urated with a bichromatic solution similar to that of the 

 pile jar. 



The zinc is hung from a small lever which it is only 

 necessary to touch lightly in order to bring the zinc in con- 

 tact with the sponge ; the circuit is then formed, the zinc 

 is attacked, and the current produced traverses the spiral, 

 which reddens and inflames the oil. The pile once 

 charged will serve for several hundred lightings. When 

 the spiral no longer becomes red hot, the sponge must be 

 replaced — a very simple operation. A\ hen the small lever 

 is not pressed upon, the zinc is raised and kept thus from 

 the action of the liquicl which the sponge of amianthus 

 absorbs. M. Desruelles constructed on the same prin- 

 ciple a lighter to gas burners, in which the pile is placed 

 at the extremity of an arm which is long or short, accord- 

 ing to the height of the burner. This small domestic 

 apparatus can be seen at the Electrical Exposition, where 

 ts practical working is shown. 



International Congress of Electricians.— 

 Professor G. F. Barker, in a letter to the American Jour- 

 | nal of Science sa> s : 



The exhibition as a whole has been a decided success. 

 It has brought together an immense mass of highly in- 

 teresting material. There are in all something over 1500 

 exhibitors, of which one half are French, 155 Belgian, 115 

 English, 114 German, 81 Italian, 72 American, 39 Aus- 

 trian, 32 Russian, 21 Swedish, 13 Swiss, 17 Spanish, 13 

 Norwegian, 11 Dutch, 5 Danish, and 2 Japanese. Of de- 

 j cided novelties, there are more in the United States sec- 

 1 tion than in any other. Edison has made a wonderful ex- 

 hibition of his inventions, and his rooms are thronged 

 continually. The principle discovered by him that an 

 electric current varies friction, the so-called motograph 

 principle, together with the applications of it practically, 

 are beautifully illustrated. The principle of the varying 

 resistance of bodies which imperfectly conduct, whenthey 

 are subjected to pressure, a principle which he was the 

 first to investigate and to apply, is exhibited in a large 

 series of instruments, one set of which traces the progress 

 of development of the carbon telephone. The system of 

 incandescent lighting which he has perfected is shown in 

 all its details, from the unique dynamo machine of lowre- 

 sistance and high electromotive force, the street conduct- 

 ors with their connections, safety-catches, expansion-caps, 

 etc., the ingenious meter and the house conductors with 

 their incombustible covering, to the fixtures with double 

 conductors and safety catches, and lastly to the incan- 

 descent lamp itself. Dolbear exhibits a new electro-static 

 telephone which performs admirably and which consists 

 simply of two thin metal plates, connected to the secon- 

 dary wire by an induction coil. They are oppositely 

 charged by the coil and so attract each other. Gray's 

 harmonic multiple telegraph is in : uccessful operation 

 and Bell's original photophone is also exhibited. The 

 most original thing exhibited in the French section is the 

 secondary battery : Piante exhibits several forms of it, 

 Faure shows the improvement which he made by cover- 

 ing the plates with minium, and lastly Meritens is work- 

 ing a still newer form, in which only lead plates are used, 

 but a large number ot them are put in a small space. In 

 the historical line the collection in the exhibition is unri- 

 valed. The pile of Volta, the electroscopes ot Galvani, the 

 thermopiles of Nobih and Melloni, the electro-magnetic 

 induction ring of Faraday, the first magneto-machine of 

 Pixii, the rheostats and telegraphs of Wheatstone, the 

 telegraphs of Soemmering, of Sttinheil and of Gauss and 

 Weber, the continuous current-machine of Pacimotti, the 

 electro-thermic and electro-motor apparatus of Becquerel, 

 the electro-capillary apparatus of Lippmann ; all these 

 and many more are here collected. And as for arc lights, 

 the exhibition at night is like day. The Brush machine 

 and light are in great favor. A large lamp of this sort 

 just put up has carbons two inches in diameter, and is 

 claimed to give a light of 80,000 candles. 



BOOKS RECEIVED. 



A Treatise on the Method of Government 

 Survey, with complete Mathematical, Astronomical 

 and Practical Instructions. By Shobal V. Cleven- 

 GER. Second Edition, rtvised. D. Van Nostrand, 23 

 Murray street, New York. 

 This excellent treatise will be found of the greatest value 

 to all engaged in government land surveying, and appears 

 to surpass all its predecessors in its compleiencss and 

 adaptability for practical woik. Dr. Clevenger is one of 

 our most esteemed contributors, and our readers are 

 aware of the thorough nature of all literary productions 

 which proceed from his pen. The present treatise on 

 government land survey is exhaustive of the subject, and 

 has been accepted by the highest authorities as an 

 authoritive manual. 



