

ELECTRO-TELEGRAPHY 229 



water. The precipitate may now be dried and bottled for use. To prepare Cyanide 

 of Gold. Dissolve 1 oz. of fine gold in 1*4 oz. of nitric acid and 2 oz. of muriatic 

 acid ; after it is dissolved add 1 quart of hot water, and precipitate with the second 

 preparation, proceeding the same as for the cyanide of silver. To prepare Cyanides 

 of Copper and Zinc. For copper, dissolve 1 oz. of sulphate of copper in 1 pint of hot 

 water. For zinc, dissolve 1 oz. of the sulphate of zinc in 1 pint of hot water, and 

 proceed the same as for cyanide of silver. The electro-plater, to insure success in 

 plating upon all metals and metallic alloys, must have two solutions of silver ; the 

 first to whiten or fix the silver to such metals as iron, steel, Britannia metal, and 

 German silver ; the second to finish the work, as any amount of silver can be deposited 

 in a reguline state from the second solution. First, or Whitening Solution. Dissolve 

 2 1 Ibs. (troy) of cyanide of potassium, 8 oz. carbonate of soda, and 5 oz. cyanide of 

 silver in one gallon of rain or distilled water. This solution should be used with 

 a compound battery, of three to ten pairs, according to the size of the work to be 

 plated. 

 sium, and 

 solution should 



plate is placed as near the surface of the articles to be plated as possible. N.B. By 

 using the first, or whitening solution, you may insure the adhesion of silver to all 

 kinds of brass, bronze, red cock-metal, type-metal, &c., without the use of mercury, 

 which is so injurious to the human system. To prepare a Solution of Gold. 

 Dissolve 4 oz. (troy) of cyanide of potassium, and 1 oz. of cyanide of gold, in 1 

 gallon of rain or distilled water. This solution is to be used warm (about 90 Fahr.) 

 with a battery of at least two cells. Gold can be deposited of various shades to suit 

 the artist, by adding to the solution of gold a small quantity of the cyanides of silver, 

 copper, or zinc, and a few drops of the hydro-sulphuret of ammonia.' 



EZiXiCTRO-PXiATXNCr BATH. See CYANIDES. 



ELECTRO-SORTING- APPARATUS. M. Froment devised an apparatus 

 for the separation of iron from matters by which it may be accompanied. The ap- 

 paratus consists of a wheel carrying on its circumference eighteen electro-magnets. 

 The iron ore, reduced and pulverised, is spread continually upon one of the extremities 

 of a cloth drawn along with it, and passed under the electro-magnets in motion. The 

 iron in the ore which has of course been brought into a magnetic state by any of the 

 processes by which this may be effected, is separated by the magnets, and the 

 impurities carried onward. See De la Eive's ' Electricity.' 



EliECTRQ-TEZiSGRAPKY. The simultaneous appearance of the electric 

 spark at the respective ends of a long conducting wire forcibly arrested the attention 

 of electricians in the early days of the science. 



A series of remarkable experiments were made by Dr. Watson, commencing on 

 July 14th, 1747; when he passed an electric discharge from the Thames bank at 

 Westminster to the opposite bank at Lambeth, by means of a wire suspended to 

 Westminster Bridge. He continued his researches ; and, on August the 5th of the 

 following year, he arranged 12,276 feet of wire at Shooter's Hill, the beginning, the 

 middle, and the end of which were led into the same apartment. He discovered that 

 the electric signs at the middle of the wire coincided in time with the discharge at the 

 two ends, proving that the passage, at least in such a length of wire, was instantaneous. 

 In reference to these results, Professor Muschenbroeck wrote to Dr. Watson : Mag- 

 nificentissimis tuis experimentis, superasti conatus omnium,' Dr. Franklin made 

 similar experiments in 1748 across the Schuylkill at Philadelphia, and in the next 

 year Du Luc repeated them across the Lake of Geneva. 



The idea of applying this property to the transmission afar of telegraph signals 

 proper was an early and natural result of these discoveries. But many onward steps 

 were necessary before the idea could assume any definite form ; and further advances 

 in knowledge were essential before the idea could be realised. 



Locked up, as it were, in all bodies, is a large store of electric force, the equilibrium 

 of which is disturbed in a greater or less degree by a variety of causes, some extremely 

 simple, others more complex ; and, according as one or other cause is in operation, 

 the conditions under which the electric force is manifested vary ; some conditions 

 being very unfavourable, and others very favourable to the object in view. 



The rapidity with which electric force traverses conductors depends upon the cir- 

 cumstances under^ which the conductors are placed; in the case of wire suspended in 

 the air, the electric force has little else to do than to travel onward and be discharged 

 from ^the far end of the wire ; in the case of buried wire, it has to disturb the 

 electric equilibrium of the gutta-percha as it travels onward, and thus suffers con- 

 siderable retardation. The greatest recorded velocity of a signal through a suspended 

 copper telegraph wire is 1,725,800 miles per second, by M. Hipp ; the lowest velocity 

 through a buried copper-wire, 750 miles per second by Faraday. Intermediate 



