498 



MECHANICAL IMPROVEMENTS. 



invention. He has discovered a method of 

 subdividing the electrical current, so that a 

 large number of small lights can be produced, 

 whose intensity depends upon their number. 

 In these smaller candles carbons are not used. 

 The current can be indefinitely subdivided, and 

 the lights made of any desired intensity, and 

 each one is as steady and uniform as any known 

 source of illumination. By his former process 

 no more than eight lamps could be illuminated 

 by an ordinary Gramme machine. His first 

 experiment on a non-combustible substance 

 was to pass the current generated by the dyna- 

 mo-electric machine through the inner wire of 

 a Ruhmkorff induction-coil, and allowing it to 

 act upon small bars of kaolin, placed between 

 the terminals of the outer coil. Obtaining a 

 low degree of luminosity, he improved his con- 

 ductors, connecting them with the edge of the 

 kaolin bar. which became white hot, emitting 

 a fine light, a very small portion of the sub- 

 stance being consumed. The light thus pro- 

 duced by the secondary wire of the induction- 

 coil has the form of a luminous band, and is 

 considerably larger than the spark produced 

 through the Ruhmkorff coil alone. By em- 

 ploying different sizes of induction-coils, the 

 intensity of the light may be varied from 1 

 to 15 Argand burners. When machines produc- 

 ing alternate currents are employed, no con- 

 tact breakers or condensers are needed for the 

 coils ; around the primary wire of the Ruhm- 

 korff coil as many secondary coils may be 

 wound as there are lights required, and each 

 of these may be extinguished or lighted inde- 

 pendently. 



Mr. Van der Weyd has devised an apparatus 

 for the utilization, for photographic purposes, 

 of the electric light generated by a magneto- 

 electric machine. The light is placed in the 

 focus of a parabolic reflector turned toward 

 the object to be photographed, which has a di- 

 ameter of 40 inches. The direct rays are stop- 

 ped by a metal disk, while the reflected rays 

 are concentrated on the object by a Fresnel 

 lens (one constructed by the superposition of 

 concentric rings of prisms), which covers the 

 mouth of the reflector. 



A new process of electro-plating has been 

 invented by Prof. A. W. Wright, of Yale Col- 

 lege. In a hollow vessel, from which the air 

 has been partially exhausted, are placed op- 

 posite to each other the two poles of an in- 

 duction-coil, between which the article to be 

 electro-plated is suspended. A small piece of 

 the metal which is to be deposited on the ar- 

 ticle is attached to the negative pole. Grove 

 cells of 3 to 6 inches are used to produce 

 a spark 2 to 3 inches long, which ren- 

 ders gaseous, or volatilizes, a portion of the 

 metal. The volatilized metal, as it condenses 

 on the cooler surface of the object of glass or 

 other material, forms a perfectly clear and even 

 deposit, which can be made as thin or as thick 

 as is desired by continuing the action of the 

 electricity a shorter or longer time. By this 



important new process mirrors of the most 

 brilliant and uniform character have been pro- 

 duced with gold, silver, platinum, bismuth, and 

 iron. Prof. Wright obtains curious colors from 

 the metals, which vary according to the thick- 

 ness of the deposit. Gold has been laid on in 

 a film of only .000183 mm. in thickness, and 

 platinum in a layer only .000174 mm. thick. 

 Prof. Wright can produce, by his process, un- 

 alterable telescopic and heliostatic mirrors, by 

 precipitating a layer of platinum upon silver. 

 In the glass globe, within which the operation 

 is performed, a vacuum is maintained with an 

 air-pump. Iron, when thus spread in an ex- 

 ceedingly thin coating, exhibits a singular 

 chemical stability, not oxidizing when exposed 

 for several months to moist air, and withstand- 

 ing for a few moments the action of nitric 

 acid ; and even when exposed to nitro-hydro- 

 chloric acid, it only exhibited the same be- 

 havior as platinum. 



Mr. Egerton, who planned a ship built on 

 pontoons, for conveying trains of cars across 

 the British Channel, has invented a tidal pier, 

 which will permit of trains running directly 

 on board at any tide. His pier is built in sec- 

 tions, supported at the points of connection 

 by pontoons, which are set in guides, and can 

 be protected from the action of the waves by 

 a breakwater. The roadway is connected with 

 the pontoons by a huge kind of lazy tongs, 

 which changes its position at every change in 

 the tide, and affords a perfectly straight though 

 not rigid road. The inventor claims that the 

 same principle can be applied with great utility 

 to all piers, and also to bridges ; and he pro- 

 poses it for the Thames, as a relief for the 

 overcrowded London Bridge, and for the Mer- 

 sey, between Liverpool and Birkenhead. 



Sir William Thomson exhibited before the 

 British Association an instrument of his in- 

 vention, with which soundings can be taken 

 on a steamer or other vessel at full speed. Or- 

 dinarily it. requires half an hour's time, and a 

 quarter of an hour's actual detention, to take 

 a sounding of less than 100 fathoms. With 

 this machine soundings have been made in 100 

 fathoms, on steamships making over 15 knots 

 an hour, in five or six minutes. The depth is 

 indicated by the pressure of the water upon a 

 column of air in a glass tube, instead of by the 

 length of line paid out. The 22-lb. sinker is 

 attached, by a 9-foot rope, to a steel piano- 

 wire 330 fathoms long, connected by an iron 

 ring with the rope. The sinker is furnished, 

 as usual, with tallow, to receive a specimen of 

 the bottom, or an impression if it is a rocky 

 bottom. Sir William Thomson also called at- 

 tention to the necessity of having continuous- 

 ly-moving magnets connected with the com- 

 pass on iron ships, to counteract the changes 

 in magnetism which occur on all iron vessels 

 in different latitudes and through the lapse of 

 time, and also to correct the compass when it 

 is disturbed, as frequently happens, by the 

 firing of guns. He showed a magnetic com- 



