172 
FESSENDEN. 
volts the electrostatic discharge from the wires uses up so 
much energy and causes such a large capacity current that 
higher voltages are impracticable. The voltage permissible 
increases with the size of the conductors, and may be in¬ 
creased also, no doubt, by wrapping the wires with a cheap 
fibre impregnated with some cheap insulating material, thus 
reducing the maximum electrostatic intensity in the air, but 
from present indications we may sa}^ that there is no proba¬ 
bility that we shall ever find it profitable to transmit power 
in large quantities over more than 150 to 200 miles. 
The past year has marked the appearance of what may be 
called the “perfect” alternating current motor in the shape 
of a condensered motor, designed by C. P. Steinmitz. Practi¬ 
cally, no more remains to be done in this line. 
The history of the alternating current motor is of interest, 
as showing how soon an imperative demand is supplied. 
The true precursor of the alternating current motor was the 
motor of Bailey, which ran by polyphase currents obtained 
by commutating direct currents. This was, however, con¬ 
sidered merely as an interesting toy. When the demand 
for an alternating current motor arose, electricians confined 
themselves to single-phase motors, as the employment of a 
number of circuits would naturally be considered objection¬ 
able. Tesla, as a perusal of his original patents shows, at¬ 
tempted to use the old whirligig motor of the laboratory, in 
which a number of magnets were alternately attracted to 
and repelled from a set number of stationary magnets. His 
improvement, as he himself states in his patent application, 
consisted in using, instead of two commutated direct cur¬ 
rents, two alternating currents, and his sole claim for a pat¬ 
ent, according to his statement contained in his application, 
is that, while, as he acknowledges, the motor is old, the use 
of an alternating current does away with the sparking caused 
by breaking the continuous current in the old way. That 
the idea of an induction motor was not contained in his in¬ 
vention is shown by the fact that in another patent he later 
states that the field must be carefully laminated, to prevent 
