276 



RECEEATIYE SCIENCE. 



luto the cup, thus prepared, pour a small 

 quantity of melted lead ; remove the film of 

 oxide, which immediately forms on its sur- 

 face, by means of a slip of paper, and, just 

 before it is cool enough to set, drop upon it 

 the florin, profile downwards. Owing to the 

 lesser specific gravity of the silver, it will 

 float, about half immersed, upon the surface 

 of the lead. In a minute or two, the contents 

 of the cup may be turned out, a process greatly 

 facilitated by the paper lining, as, without 

 this, the metal might stick to the earthen- 

 ware, and possibly break it. If, on examina- 

 tion, the impression is found to be imperfect, 

 from the presence of air-bubbles, or from the 

 intrusion of any foreign substance, the metal 

 must be remelted, and the process repeated. 

 If, however, it be found perfect, we may 

 proceed. 



Let A A (Fig. 1) represent the mould thus 

 produced ; the wire (c c) should now be 



Fig. 1. 



fixed to it, either by means of a drop of solder, 

 or, if a soldering-bit be not at hand, by means 

 of sealing-wax. In the latter case, take par- 

 ticular care to clean the surfaces which come 

 in contact both of the lead and copper-wire, 

 by rubbing them with sand-paper. If, how- 

 ever, the fusible alloy mentioned in the pre- 

 ceding foot-note be used, a far preferable way 

 of attaching the wire would be thus : — Clean 

 the end of the wire with sand-paper, hold it 

 in the flame of a candle, so as to leave a 

 quarter of an inch of the end unblackened, 

 while the portion immersed in the flame be- 



comes red hot. Now touch the clean end 

 with a little powdered rosin, and instantly 

 apply it to the mould (at c) with a gentle 

 pressure. The metal will readily yield, and 

 the wire will become firmly embedded into it 

 without further trouble. 



On account of the facility with which 

 fusible metal is thus operated upon, and the 

 low temperature at which it melts, it will 

 generally be worth the amateur's while to 

 procure this alloy at starting. Nevertheless, 

 just for a first trial of one's hand at electro- 

 typing, lead wiU do very well. 



But it is not desirable to deposit the cop- 

 per upon the entire surface of the mould thus 

 prepared ; and, in order to confine the depo- 

 sition to the impression, it becomes necessary 

 to cover the remaining portion with some 

 nonconducting material. 



For this purpose, tallow or wax may be 

 used. It should be melted and rubbed over 

 the mould, so as to cover every portion, ex- 

 cept the central depression, and a narrow rim 

 round it, as shown at d d (Fig. 1) ; in doing 

 which, exercise the utmost care to prevent 

 the impression from being soiled, or even 

 touched by the fingers, for on the fulfilment 

 of this condition will the success of the expe- 

 riment greatly depend. The mould being 

 thus prepared, we may turn our attention to 

 the construction of the voltaic apparatus, and 

 the cell for deposition. 



At the end e of the wire (Fig. 1), a plate 

 of zinc, about three inches long and an inch 

 and a half wide, is now to be attached. It 

 will be sufficient to punch a small hole in one 

 end of the plate, to clean that end with a 

 piece of sand-paper, and also the end of the 

 copper-wire, and then to run the latter through 

 the hole in the plate, and secure it by tightly 

 twisting. This process of cleaning should bo 

 carefully observed, in order to insure a per- 

 fect contact between the two metals. Now 

 for the cell. 



A stoneware jar, of from a pint to a quart 

 capacity, will do very well for coins and me- 



