REFINING OF COPPER AND LEAD. 199 



The following contain some details respecting the electrical 

 installation proper : 



The first continuous-current machine executed for M. 

 Wohlwill is illustrated (Fig. 32). It is provided . with two 

 collectors and four brushes. Each collector has twenty sections. 

 The spirals of the bobbin are each composed of seven strips of 

 copper 10 millimetres wide by 3 millimetres thick. Forty 

 groups of copper ribbon correspond to the forty sections of the 

 two collectors, so that each spiral is composed of two iden- 

 tical half spires juxtaposed and soldered at their extremities to 

 a radiating piece which connects them to one of the sections of 

 the double collector. The inducted ring is therefore com- 

 posed of forty partial bobbins, of which twenty are connected to 

 the right-hand side, and twenty to the left-hand side collector. 



The total resistance of the induced bobbin is '0004 ohm. 

 When the two parts are joined in parallel this resistance is 

 only '0001 ohm. 



The electromotive force, with a speed of 500 revolutions per 

 minute, is equal to 8 volts for the coupling in series, and to 

 4 volts for the coupling in parallel. 



The eight electro-magnets of this machine have iron cores 

 120 millimetres in diameter, and 410 millimetres in length. 

 On these cores are wound thirty-two turns of sheet copper of 

 the same width as the length of the electro, and a thickness 

 of 1 * 1 millimetre. The resistance of the eight inductors in one 

 single circuit is "00142 ohm. When the electros are joined in 

 two series, their resistance becomes '00028 ohm. The total 

 resistance of the machine is therefore * 00038 ohm in quantity, 

 and '00182 ohm in tension. 



The total weight of copper used in the construction of 

 the induced and the inducting coils is 735 kilogrammes. The 

 machine is 1 '50 metre long, "75 metre wide, and 1 metre high. 

 It weighs about 2500 kilogrammes. Its normal capacity is 

 3000 amperes when coupled in quantity, and 1500 amperes 

 when coupled in tension. Its total production is therefore 

 12,000 watts per second. 



The baths number forty, and are associated in two series of 

 twenty. The surface of anodes immersed in each bath is about 



