282 



ELECTRICITY. 



received from the central disk, and communi- 

 cates it in the form of a stroke by a connecting 

 rod to a crank on the paddle-shaft. The end 

 of the moving bar also sets to work the dis- 

 tributors for alternately establishing and cutting 

 off the electric communication between the 

 magnets and the battery. In all there will be 

 sixteen elements of Bunsen':?, and the force of 

 the machine is about one man power. The pad- 

 dle-wheels are two feet six inches in diameter. 

 Popular Science Review, July, 1866. 



Application of Electricity to Sounding at 

 Sea. M. Hedouin, of Lyons, has invented a 

 sounding apparatus, consisting of a line within 

 the whole length of which. run two conducting 

 wires, the upper ends of which are connected 

 respectively with the poles of a galvanic battery 

 placed in the ship. The lower ends are never 

 connected, and, consequently, the circuit is never 

 complete until the lead touches bottom. "When 

 this occurs, the lower portion of it, which 

 slides into the upper, presses a small piece of 

 metal against the two lower ends of the wires. 

 The instant the circuit is thus completed, a bell 

 is rang by an ordinary electro-magnetic appa- 

 ratus, and thus the attention of the sounder is 

 drawn to the fact that the lead has touched 

 bottom. Besides this, a ratchet is, by similar 

 means, thrown into action, and instantly arrests 

 the descent of the line from the reel on which 

 it is coiled ; and thus, even the attention of the 

 sounder is rendered of less importance. If there 

 is danger of the vessel getting into shallow 

 water, or among sunken rocks, a sounding line 

 of given length, suspended from the vessel, will 

 give instant notice of danger. 



Improved, Electrotype Process. Christofle 

 and Bouillet of Paris have introduced great im- 

 provements into the electrotype process. They 

 add to the silver bath sulphuret of carbon or 

 an alkaline sulphuret which produces a small 

 quantity of sulphate of silver, and this, for 

 some unexplained reason, causes the silver de- 

 posit to be as brilliant as if it had been care- 

 fully burnished. They add to the common 

 sulphate of copper bath a moderate quantity of 

 gelatine, which causes the copper deposit to be 

 as compact and dense as the best rolled sheet- 

 copper. They also secure great economy in 

 their operations by attaching plates of lead to 

 the platinum wire which forms the interior 

 skeleton of the mould used for the production 

 of articles in relief. 



New Electric Fire Alarm. M. Robert Hou- 

 din has invented an electric alarm of extreme 

 delicacy. It is formed by soldering together a 

 blade of copper and another of steel, fixing 

 one end of the compound blade to a board, 

 along which it lies parallel but not in contact. 

 Near the free extremity of the blade is a 

 metallic knob in conducting communication 

 with one pole of a galvanic battery, the free 

 end of the compound blade being in connection 

 with the other. "When the temperature of the 

 surrounding air (from a fire breaking out) is 

 increased, the blade becomes curved, and, com- 



ing in ccntact with the metallic knob, the bat- 

 tery connection is complete. This causes a 

 small bell to ring. The apparatus is so sensi 

 tive that a lighted cigar or taper placed within 

 a few inches of it will cause a ringing of the 

 bell. 



Cheap Electric Battery. M. Gerardin, in a 

 note to the French Academy of Science, pro- 

 poses to obtain a battery of feeble tension, but 

 of considerable quantity, and cheap, by substi- 

 tuting 'in the Bunsen battery, chippings of 

 wrought or cast iron in place of zinc. An 

 iron plate in contact with them serves as a 

 conductor, and the exciting liquid is ordinary 

 water. Ill the porous cell, the Bunsen carbon, 

 made of gas coke, pulverized and cemented 

 by paraffine, is immersed in a solution of per- 

 chloride of iron, to which some aqua regia is 

 added. The pile can be made of largo dimen- 

 sions, and it is said that great quantities of 

 electricity can be obtained from it at a very 

 small price. 



The Holts Electrical Machine. This is a 

 recent invention for the production of elec- 

 tricity. Two glass plates made of thin plate- 

 glass varnished with shellac are placed in close 

 proximity to each other, one of them being 

 permanent and the other movable and rotated 

 by the ordinary winch and pulley- wheel. The 

 movable plate is a little smaller than the other, 

 and supported on an axle which passes through 

 a large central hole in the other. The latter 

 plate, besides the central hole, has four other 

 holes, of a circular shape. At the side of each 

 of these openings is pasted a strip of paper 

 with a point of card projecting into it. The 

 rotation of the movable plate is in the direc- 

 tion from point to base of the card projections. 

 Opposite to each of the paper strips (but with 

 the revolving plate) is a brass comb or collector 

 supported in a crosspiece of vulcanite by ap- 

 propriate brass rods. The four brass collectors 

 may be united in various ways by bent wires 

 for different effects. The movable plate being 

 put in rotation, the paper strips are charged by 

 touching them with a piece of vulcanite, ex- 

 cited by a stroke over a rabbit-skin, and at 

 once the whole machine is in activity and giv- 

 ing out sparks of great volume and intensity, 

 which may be continued for an indefinite time 

 without further charging. There are no rub- 

 bing parts in the machine, the whole effect be- 

 ing developed by induction, or the disturbance 

 produced in the electric fluids by the repulsion 

 of like and attraction of unlike kinds. Yet 

 this machine exhibits all the effects of fractional 

 electricity. A torrent of sparks can be pro- 

 duced between the terminal balls, each giving 

 a report like the explosion of a torpedo ; and, 

 by a different adjustment, a continuous jet of 

 electric fire is displayed, seeming to pass in a 

 tassel of purple light trimmed witli golden 

 beads, and emitting a hissing sound like that 

 of escaping steam. The Geissler tubes are 

 operated by the Holtz machine with fine effect. 

 Jour. Frank. Institute, October, 1866, 



