A/A' WILLIAM SIEMENS, F.R.S. 193 



: on, and electricity enough to work two lights could be sent 

 throimli the double area to a double distance. The moment that 

 was done the conductor was increased, for the power was trans- 

 inittrcl only in the proportion of the increase of the length ; but 

 that was not enough. The electric conductor did not resist the 

 motion of electricity in the same manner as a pipe resisted the 

 flow of liquid through it, but an Ohm's resistance was an Ohm's 

 resistance for a larger as well as for a smaller current flowing 

 through it, which resistance was only increased by a rise of 

 temperature in the conductor. This rise of temperature was kept 

 uo\vn by dissipation of heat from the conductor; or considering 

 that the longer and doubled conductor would possess four times 

 the amount of surface for the dissipation of heat than the single 

 and short conductor, it would be capable of transmitting four 

 times the amount of electric current. It might therefore be said 

 that it was no dearer to transmit electro-motive force to the 

 greater than to the smaller distance, as regarded weight and cost 

 of conductor, a result which seemed startling, but which he never- 

 theless ventured to put forward with considerable confidence. In 

 uniting the two longer conductors into one, the surface would, 

 however, be increased only in the ratio of ^/2 : 1 ; therefore the 

 relative transmitting power between the longer and shorter con- 

 ductor would, strictly speaking, be increased to the ratio of 

 1 : '1 /27or 1 : 2'83, and the longer conductor would be dearer 

 than the shorter per unit of electro-motive force transmitted in 

 the proportion of 4 : 2*83. 



In the discussion of the Paper 



" ON THE TELEGRAPH ROUTES BETWEEN ENGLAND 

 AND INDIA," by MAJOR BATEMAN CHAMPAIN, R.E., 



DR. SIEMENS, F.R.S., * said the paper was remarkable for its 

 clearness and candour. Every one who had contributed towards 



* Excerpt Journal of the Society of Arts, Vol. XXVI. 1877-78, p. 532. 

 VOL. II. O 



