.<?//? WILLIAM SIEMENS, F.R.S. 223 



Captain Bucknill points out very forcibly that in the experi- 

 i miits carried out last spring at the South Forelands by Professor 

 Tvmlall and Mr. Douglass, for the Trinity House, great loss of 

 illuminative effect was observed to result from an increase of 

 i-Ii < -i rical resistance of the metallic conductor through which the 

 ctinvnt is communicated to the lamp from the dynamo-electrical 

 machine. This loss was relatively greater in the case of the 

 Siemens than in that of the Gramme machine, for the simple 

 reason that the former machine had been constructed with little 

 resistance in its own coils, the intention having been to produce 

 quantity rather than intensity of effects. Electricians will readily 

 follow me when I say that the internal resistance of the dynamo 

 machine, or the size, thickness, and length of the insulated wire 

 employed in its construction, should always be made proportionate 

 to the external resistance, comprising the lamp and its leading 

 wires, in order to obtain a maximum effect. It would be as wrong 

 and wasteful to employ a dynamo machine of considerable internal 

 resistance to work through a circuit of little resistance as it is to 

 attempt a greater external resistance with a machine of little 

 internal resistance, such, for instance, as would be suitable for 

 effecting metallic precipitation. 



As an example of producing electric light at a considerable distance 

 I may here mention the interesting application by Sir William 

 Armstrong, who lights his library at Craigside successfully with a 

 current produced by a waterfall 1500 yards distant. A Siemens 

 dynamo-machine of the smallest type is employed to generate the 

 current, and this is conveyed to the lamp and back again to the 

 machine by a copper wire of three-tenths of an inch diameter, 

 suspended at intervals from iron posts, and representing a resist- 

 ance of 1^ units or Ohms. If a waterpipe or the metals of a 

 railway or tramway could have been pressed into service for 

 the return of the current, one-half of the line-resistance might 

 have been saved, or the distance of the light from the source 

 might have been increased to nearly 3000 yards. This would, 

 therefore, be the limit of distance to which the light might be 

 carried in a town, where the water and gas pipes constitute a 

 perfect return wire for any number of electric circuits. 



Sir William Armstrong now intends to put up a medium-sized 

 dynamo-machine at the source of water power, and to utilise the 



