REFINIXG OP COPPER AND LEAD. 221 



erroneous conclusion, sometimes used a current of 6*3 amperes 

 per 1600 square centimetres, which corresponds to 1 ampere 

 per 254 square centimetres, or 30 amperes per square metre ; 

 and sometimes the same current of 6*3 amperes for 6 square 

 metres, that is to say approximately 1 ampere per square metre. 

 Under these conditions, the deposition was naturally regular, 

 fine and cohesive, and the thickness obtained in one hour varied 

 from 004 millimetre to '0001 millimetre. 



At Hamburg, M. Wohlwill, having always had in view the 

 object of economising the motive power, has also been led to 

 operate with large surfaces of cathodes, obtaining, therefore, small 

 thicknesses of copper depositions per hour, In his first installa- 

 tion the large Gramme machine deposits 30 '50 kilogrammes 

 per hour on 1200 square metres of surface, that is to say 25*4 

 grammes per square metre. The thickness of the copper pre- 

 cipitated on the cathodes is therefore 003 millimetre per hour. 

 In the two installations which followed, this result was still 

 very much reduced since the deposit per hour did not exceed 

 37 ' 50 kilogrammes of copper on 3600 square metres of cathodes, 

 which corresponds to an approximate thickness of * 001 milli- 

 metre in the same time. 



At Messrs. Oeschger and Mesdach's, the production is 700 

 kilogrammes of copper in 24 hours, or 29 kilogrammes per hour, 

 with 1200 square metres of surface of cathodes. The thickness 

 of the deposition is approximately 003 millimetre per hour. 



At Marseilles, M. Hilarion Roux precipitates 10*4 kilo- 

 grammes of copper per hour on 900 square metres of cathodes, 

 or 11 '44 grammes per square metre. The thickness of the 

 deposition is therefore '001144 millimetre per hour. 



The Elliott Metal Company at Birmingham have five in- 

 stallations which precipitate each 13 kilogrammes of copper 

 on 144 square metres of cathodes, or 90 grammes per square 

 metre. The thickness of the deposition is, in the five installa- 

 tions, "01 millimetre per hour. 



In M. Michel's factory in Paris, electrotypes 1 millimetre 

 thick are obtained in five hours, which correspond to * 02 milli- 

 metre per hour. 



It would be useless to multiply the examples, for in all those 



