1912] on Electricity Supply : Past, Present and Future. 



435 



Porter engine of loO horse-power, which shows that even in 1882 

 idea> had not progressed very far beyond those ah'eady aUuded to in 

 connection with Liverpool three years earlier. The design of these 

 early Edison machines, with their mnltiple-magnet limbs each with 

 its separate winding, is also illustrative of the ignorance then pre- 

 vailing on electro-magnetic subjects, it being obvious in the light 

 of modern knowledge that the arrangement was altogether inefficient 

 and absurd. It was the late Dr. John Hopkinson who first put the 

 design of continuous-current dynamos and their magnetic circuits 

 on a sure foundation. 



Fig. 2. — Edison Dynamo, used on Holboen Viaduct in 1882. 



In the same year we find the Gordon alternating dynamos, then 

 considered of very large size, installed to supply electricity for the 

 lighting of Paddington Ptailway Station and Hotel. It is only quite 

 recently that the use of these machines was discontinued. 



In November 1882 we have Sir William Siemens, in his opening 

 address as Chairman of the Society of Arts, discussing in considerable 

 detail the supply of electricity for general purposes in London, and 

 his opinions and figures are really very interesting in the light of 

 how matters have actually turned out. His main difficulty appears 

 to have been that of the economic distribution of the electricity for 

 the general public and private lighting of London with the low- 

 pressure incandescent lamps which were then in vogue, and in the 

 absence of high-tension transmission and of distribution on the three- 

 wire system, which have since become so general and enable much 

 greater distances to be covered with a given loss. As a result, he 



Vol. XX. (No, 106) ^ 2 g 



