PHACTICALDIKECTIOXS.] UNDULATORY FORCES. ELECTRO-METALLURGY. 



213 



65. General Arrangement of Electro-Deposition. The 

 practical part will be best arranged by beginning at the 

 very commencement ; and assuming the reader to be 

 without materials or apparatus of any kind that he has 

 to provide a workshop, prepare his solutions, batteries, 

 scouring and cleaning apparatus ; that he has to clean 

 his articles for receiving deposits, and prepare his 

 materials for moulds, before he can commence the pro- 

 cess of deposition, gradually acquiring a knowledge, as 

 he proceeds, of the kind of depositing process best fitted 

 for his purpose ; of the most suitable source of depositing 

 power ; the best solutions ; the best recipes for making 

 solutions; the construction of voltaic batteries and of 

 magneto-electric machines ; the rules for regulating the 

 currents of electricity, and the character of the deposited 

 metals ; rules for depositing metals generally, as well as 

 for cleaning and preparing metal articles to receive 

 deposits; copying works of art by moulding; preparation 

 of moulds for receiving deposits; making solutions for 

 ordinary coppering, silvering, and gilding; and for the 

 management of those solutions; information on all 

 these points it will be our task to supply. 



66. First Considerations. The first step in practice 

 is, to consider the probable magnitude of the operations 

 to be carried on, and to provide rooms of suitable size. 

 These should be upon the ground-floor (except for elec- 

 tro-gilding), well lighted and ventilated, with con- 

 veniences for the erection of boilers and drying flues, for 

 placing washing-troughs, depositing vats and batteries, 

 and for the escape of unwholesome vapours ; there should 

 also be ready access to a plentiful supply of clean water. 

 The establishment should consist of at least three rooms, 

 and an open yard with an outhouse ; an upper or more 

 private room for gilding, a ground-floor room for silver- 

 ing, and another ground-floor room for the coarser work, 

 such as coppering, brassing, and the preparation of the 

 larger and coarser articles for receiving deposits. The 

 outhouse is for the batteries, and the yard for washing 

 the battery cells. If a magneto-electric machine be 

 employed, an additional small, dry, and clean apartment 

 will be required, which should be reserved for it alone. 



67. Boilers, Furnaces. For the purpose of general 

 deposition, several large iron boilers, with furnaces 

 beneath, either in the coppering-room or in close prox- 

 imity to the silvering-room, are required ; these are to 

 contain solutions of caustic potash for cleaning articles. 

 A low furnace should be erected between those rooms, 

 having a long horizontal flue covered with plates of iron 

 for drying deposited or plated articles upon ; the room 

 for coppering should be furnished either with a low 

 furnace or stove for heating the solutions used fur cop- 

 pering or brassing iron. Each room, whether for cop- 

 pering, silvering, or gilding, should be provided with a 

 tap of running water, and a leaden trough beneath, for 

 washing the smaller articles; and the coppering-room 

 should be furnished with one or two large wooden tubs 

 or troughs, filled with water, for washing articles of 

 larger size. This room and the outhouse should contain 

 a number of large stoneware pans and jars, oval and 

 round, of different sizes and proportions, to receive the 

 various "pickling" and "dipping" liquids, acids, or 

 "spent solutions." Several large iron trays, filled with 

 sawdust, should also bo provided and fitted to the 

 furnace flue, for drying plated and deposited articles 

 upon. Each of the rooms should be provided with a 

 "scratch-brush lathe," for scouring the various articles. 

 The gOding-nxm should have several small stoves for 



ii'.; gilding solutions, or, in lieu thereof, several 

 iron tripods, with large gas-burners beneath. The silver- 

 ing ana coppcring-rooms should each be provided with 

 one or two pairs of large and well-insulated copper wires, 

 proceeding from the depositing vats to the batteries 

 outside. The gilding-room will not require these, small 

 batteries only being used in it, which are kept in the 

 same room. 



68. Sources of Electricity. A point for early conside- 

 ration will be, whether a magneto-electric machine or 

 voltaic batteries are to be used as the source of de- 

 positing power. The choice of either will depend very 



much upon the degree of confidence the operator pos- 

 sesses in each source of electricity, upon its expense, 

 and whether or not motive power to drive the former, is 

 readily and constantly available at a moderate coat. 

 Voltaic batteries are readily obtained, and worked in 

 almost any situation. We will suppose, for the purpose 

 of explanation, that the operator has resolved to use both 

 a magneto-electric machine and voltaic batteries. 



69. Construction of Magneto- Electric Machine. The 

 simplest form of apparatus for generating current elec- 

 tricity by the joint influence of magnetism and motion, 

 has been already described (15) ; but the apparatus re- 

 quired for practical purposes is far more elaborate and 

 costly in its construction. A (Fig 80) is a strong frame- 

 work of wood ; B, B, B, B, are four bundles of power- 

 Fig- so 



ful horse-shoe magnets, firmly fixed to the wooden 

 frame; is an axle driven very rapidly by steaui- 

 power; the axle carries two brass circles, upon which, at 

 right angles, are firmly fixed four round bars of pure 

 soft iron, B, C, D, E (Fig. 82), equal in length to the 

 distance asunder of the poles of each magnet ; upon each 

 of these is coiled a long piece of thick copper wire, the 

 wire being covered with cotton to insulate its coils from 

 each other ; the ends of these wires are connected with 

 four semicircular pieces, formed of a piece of brass tube, 

 fixed upon the axle C, but insulated from it and from 

 each other (Fig. 81) by a tube of hard wood or gutta- 

 percha : by rotation of the iron armatures past the poles 



Fig. 81. 



of the magnets, currents of electricity are generated in 

 the wires in one direction as they are approaching the 

 magnets, and in an opposite direction as they recede 

 from them : to collect those currents and convey them 

 to the depositing vat, also to throw them all into one 

 uniform direction, two brass springs, D E (Fig. 81), press 

 against the semicircles of brass during their revolution, 

 and are so arranged at their points of mutual contact, 

 that, just at the moment that the currents are changed 

 in direction by the armatures passing the magnets, the 

 revolution of the axle causes the points of contact of the 

 springs to pass from one pair of the semicircles to the 

 other ; and thus, by reversing the connection at the 

 moment the direction of the current is changed, a 

 uniform direction of currents is obtained in the wires 

 beyond. 



To explain the action of this machine more fully, wo 

 will suppose NS, NS (Fig. 82) to represent those poles 

 of the compound horse-shoe magnets which are placed 

 facing the observer in the elevation (Fig. 80) ; A in Fig. 

 82, is the axle, and B, C, D, and E are the ends of the 

 four horizontal round iron bars or armatures, moving 

 in the direction of the largo arrows. When a bar of 

 soft iron, having a coil of insulated wire wound upon 

 it, is moving towards a pole of a magnet, a current of 



