^rd March, 1885. 



R. Lloyd Patterson, Esq., J.P., in the Chair. 



J. H. Greenhill, Esq., read a Paper on 



ELECTRIC LIGHT AND TRANSMISSION OF POWER 

 BY ELECTRICITY. 



And Repeated {by request of the Council) 011 $th March, when 

 Dr. Everett, F.R.S., presided. 



Frictional Electricity is always of high tension, but of small 

 quantity. Thermo-Electricity has, up to the present, been of 

 comparatively low tension, but of large quantity, whereas Voltaic 

 and Magnetic Electricity may combine within certain limits 

 both tension and quantity. 



Metals in their relation as conductors of electricity may be 

 compared to pipes for the conveyance of water, but with this 

 notable difference, that whereas pipes of a given diameter or bore, 

 whether made of lead, iron, copper, or fire-clay, will convey an 

 equal quantity of water at a given pressure, metallic conductors 

 of electricity vary enormously in this respect. For instance, a 

 pure copper wire will conduct about seven times as much 

 electricity of a given tension or pressure as an iron wire of the 

 same size ; hence if iron cables were used instead of copper, they 

 would require to be of much larger size where much current 

 would be passed along, as in the case of central district lighting. 

 No economy in the first cost would therefore arise, and it is this 

 difficulty which operates* so strongly in preventing stations for 

 the supply of electricity being established. 



