ELECTRICITY. 



241 



to exceed. "When the mercury rises to this 

 point the circuit is completed, and notice is 

 given by the ringing of the bell. The same 

 battery and bell will serve for the two instru- 

 ments, but it will be necessary to interpose a 

 commutator to ascertain through which cir- 

 cuit the current is passing, and whether a rise 

 or fall is indicated when the bell is rung. 



Electric Beacons. Experiments have been 

 conducted by Mr. Thomas Stevenson, of Edin- 

 burgh, with a view of testing the practicability 

 of illuminating beacons and buoys at sea with 

 the electric light, produced by means of a bat- 

 tery on shore. A submarine cable, fully half a 

 mile long, was laid between the East break- 

 water of Granton Harbor and ths chain pier 

 at Trinity. The operator occupied a station 

 near the centre of the breakwater, and the 

 light was shown at the point of 'the pier, in 

 front of an ordinary light-house reflector, pro- 

 ducing a most brilliant flash. The flashes were 

 emitted with great rapidity ; as many as 500 

 can be transmitted in a minute, but the machine 

 can be regulated to send one every second, or 

 at any other desired interval. The experiments 

 were witnessed by gentlemen connected with 

 the Board of Trade and Trinity House, and 

 gave them great satisfaction. 



A Phono-electroscope. This is the name of 

 an instrument invented by Mr. Edwin Smith, 

 of England, to illustrate the heating power of 

 the voltaic current. It consists of a rectangular 

 wooden box, ten inches by five, two steel or 

 platinum wires stretched from end to end, a 

 small spindle carrying two quill plectra, and 

 an eccentric wheel for making and breaking 

 the current through one of the wires. The 

 wheel turns under a brass spring, which plays 

 upon a button. The spring is connected with 

 one electrode of the battery, the button with 

 the wire nearest to it, and this wire with the 

 other electrode. To exhibit the use of the in- 

 strument : First, tighten the wires, by means of 

 the milled-headed screws, to unison, to about 

 the pitch of middle C. ; then turn the spindle 

 so as to sound the two notes in succession be- 

 fore the eccentric wheel makes the circuit. 

 After these have sounded in unison, turn the 

 spindle a little more ; the circuit is made by 

 wheel and spring, and presently the plectra 

 play a second time on the wires, which now 

 sound, with an interval of a tone or more, ac- 

 cording to the quantity of electricity which has 

 passed through one of them. By regulating 

 the time between the instant when the wires 

 sound in unison and the instant when they 

 sound again, and noticing the musical interval 

 caused by one of them becoming flat, we have 

 an audible measure of the expansion of the 

 connected wire, of the temperature to which it 

 has been raised, and of the quantity of electri- 

 city which has traversed it to produce that 

 effect. By continuing the movement, the inter- 

 val between the notes will increase, and, at 

 last, the wire operated on will become too 

 slack to sound at all. If connection with the 

 VOL. ix. 16. A 



battery be now broken, and the heated wire 

 be allowed to cool, its note will be heard to 

 rise by degrees to its original pitch. With a 

 single pair of plates, the phono-electroscope 

 answers well. The experiment is a striking 

 one in a lecture-room, very instructive, and 

 easily managed. The apparatus is so simple 

 that any one almost may make it for himself. 



Electro-deposition of Copper and Brass. 

 An invention has been patented by Mr. "W. H. 

 Walenn, of England, to make electro-deposits 

 of copper and brass upon iron, or other sub- 

 stances, with less battery power, and greater 

 economy, than formerly. A solution for de- 

 positing brass is made as follows : crystallized 

 sulphate of zinc (1 part by weight), and crystal- 

 lized nitrate of copper (2 parts), are dissolved 

 in the smallest quantity of water that is 

 possible. Sufficient strong ammonia-water is 

 added to precipitate, and then fully redis- 

 solve the oxides. The purple tint of this solu- 

 tion is removed by a standard solution of cya- 

 nide of potassium. The resulting solution 

 should be left to stand for a day or two, and 

 may then be worked with from one to three 

 battery-cells, using heat if a brass anode be 

 employed. Or porous cell-arrangements may 

 be introduced, the hydrated oxides of copper 

 and zinc being from time to time supplied, 

 and, if necessary, ammoniuret of copper being 

 added. Ammonia-water and a standard solu- 

 tion of cyanide of potassium should be added 

 occasionally to the depositing liquid, in order 

 to keep the salts of copper and zinc well in 

 solution. The hydrated oxides of the metals 

 are mixed and thoroughly incorporated in the 

 proportion of two parts by weight of the copper 

 oxide to one part of the zinc oxide before 

 going into the solution. During working, little 

 or no hydrogen should be evolved. Various 

 modifications of the process are described by 

 the inventor, but the one already mentioned 

 appears to be the simplest. An electro-deposit 

 of copper is made by charging the solvent solu- 

 tion with about one part of sulphate of zinc 

 to ten or twenty parts of sulphate of copper. 

 The addition of sulphate of zinc to acid solu- 

 tions for depositing copper has long been 

 known to improve the quality of the deposit 

 the zinc toughening the copper as deposited. 

 Mr. Walenn has also discovered that the addi- 

 tion of a small quantity of bisulphide of carbon 

 to a solution containing one Ib. of sulphate of 

 copper to the gallon, and an ounce or two of 

 sulphate of zinc to the gallon, imparts a silky 

 and bright appearance to the cupreous deposit. 



The Electric Light for photographing with 

 the Microscope. A Washington correspondent 

 of the Philadelphia Press gives an interesting 

 account of experiments made by Dr. Wood- 

 ward, of the Army Medical Museum, to pro- 

 cure magnified photographs of objects by means 

 of the electric light. The writer says : 



For the production of the electric light he uses the 

 Duboscq lamp, moved by a battery of fifty small 

 Grove's elements. In this way lie finds, not only that 



