Manchester Memoirs^ Vol. Ixiii. (1920) No. 5 5 



current is there rectified and furnishes an exciting or minor 

 current for the electro-magnets. The remainder of the armature 

 bobbins supply an alternating current that is collected by the 

 brushes on the slip-rings. This major current may, if desired, 

 be rectified by replacing the rings by a second commutator. 

 When driven at 500 revolutions per minute the machine melted 

 8 feet of iron wire 0-065 ^"- ii^ diameter or ran two arc lamps 

 in series. At 1,000 revolutions per minute 12 feet of iron wire 

 0-075 "''• diameter could be fused. A comparison between the 

 power of the new machine and that of the 10 in. old type showed 

 that it was capable of giving a double amount of power with 

 less than one-fourth of the weight of materials necessary to 

 construct the 10 in. machine. 



Henry Wilde had thus produced two commercial types of 

 generator, which could be used to replace the primary batteries 

 used in electro-chemistry, and for arc lighting. 



Between 1866 and 1877 he sold machines for the following 

 purposes : — 



No. of Machines. 



Electric light for lighthouses and searchlights ... 



Electric light for photographic purposes 



Electro-deposition of metals 



Electrical bleaching of sugar and of linen 



Electro-Che7nlcal Work. 



The great demand for machines for electro -chemical purposes 

 revived Wilde's interest in these applications of electricity, and 

 he commenced experiments in his works. In 187 1 he secured a 

 patent for the coppering of iron tubes so that they were protected 

 against corrosion; and the firm did a considerable business in 

 supplying coppered tubes. In six years (1871-1877), 25,726 iron 

 tubes and 1,521 steel " doctors" were coppered. 



In 1875 Wilde secured a patent of very considerable impor- 

 tance, which became very remunerative. It was for the purpose 

 of making the rollers used in calico printing. An iron roller is 

 first coated with a thin layer of copper in a hot cyanide bath, 

 and afterwards is mounted so as to be capable of being revolved 

 vertically in a solution of copper sulphate. This enabled a 

 much higher current density to be used and the rate of deposi- 

 tion to be greatly increased; and yet a very good quality of 

 copper could be obtained, which was of even thickness. The 

 specification also included a screw propeller for keeping the 

 electrolyte at a uniform density. The patent was applied in a 

 number of works, and was ultimately sold to the Broughton 

 Coppei* Company Limited in 1880, who extended its use for the 

 coating of hydrauhc rams, etc. Two years previously, Henry 

 Wilde had entered into an agreement with Sir Joseph C. Lee of 

 Manchester for the use of the patent process of coppering. 



