by Means of Electricity . 
1879.] 
185 
thousandfold recovery at the other end , without increase of current. 
And the same would be true for any other proportion. 
Since the electromotive force is increased in proportion to 
the increase of power transmission, the insulation of the 
cable and machines would require to be proportionally 
increased. 
As an example, it may be mentioned that a dynamo- 
eleCtric machine used for the purpose of A in the figure, may 
have a resistance of say 40 ohms, and produce an electro- 
motive force of say 40 volts. Such a machine might require 
from three to five horse-power when used in connection with 
a suitable motor, B, for recovery of the power transmitted. 
If the resistance of the motor B be say 60 ohms, and the 
cable transmitting the currents a distance of 1 mile be 
1 ohm, then the current — 
C= 4 °° — 4 °° 
60+40 + 1 101* 
If, now, one thousand machines and one thousand motors, 
and a thousand miles of cable, each of the same relative 
resistances, be used, the current — 
q_ 1000 X400 
1000 x IOI ? 
which has manifestly the same value as before. If our 
supposition of the power used to drive one machine be 
correct, then from 3000 to 5000 horse-power would be ex- 
pended in driving the machines, and possibly about 50 per 
cent of this amount recovered. Then we have from 1500 to 
2000 horse-power conveyed a distance of 1000 miles. What 
diameter of copper cable will be required for such trans- 
mission ? Since this cable is supposed to have the resistance 
of 1 ohm to the mile, calculation would place the requisite 
thickness at about £ inch. If, however, the distance be 
only 500 miles, then the resistance per mile maybe doubled, 
or the section of the cable be decreased one-half, or its 
diameter will be less than one-fifth of an inch. 
For the consumption of 1,000,000 horse-power a cable of 
about 3 inches in diameter would suffice under the same 
conditions. However, by producing a much higher electro- 
motive force, the section of the cable could be proportionally 
reduced, until the theoretical estimates which we have given 
in the first part of this paper might be fulfilled. The enor- 
mous electromotive force required in the above calculation 
would, however, necessitate such perfect insulation of the 
