ectromotive force lags 90 degrees behind the impressed electromotive
force. And so, in general, the natures of these two properties are
opposite. In a cable, the wires are so close together that their
induction is negligible, while their capacity is so great as to limit
commercial transmission through a cable having .06 microfarads per
mile capacity and 94 ohms loop resistance per mile, to a distance of
about 30 miles. In the case of open wires spaced 12 inches apart, the
limit of commercial transmission is greater, not only because the
wires are larger, but because the capacity is lower and the inductance
higher.

Table I shows-the practical limiting conversation distance over
uniform lines with present standard telephone apparatus.

TABLE I

Limiting Transmission Distances

+-----------------------------+----------------------+
| SIZE AND GAUGE OF WIRE | LIMITING DISTANCE |
+-----------------------------+----------------------+
| No. 8 B. W. G. copper | 900 miles |
| 10 B. W. G. copper | 700 miles |
| 10 B. & S. copper | 400 miles |
| 12 N. B. S. copper | 400 miles |
| 12 B. & S. copper | 240 miles |
| 14 N. B. S. copper | 240 miles |
| 8 B. W. G. iron | 135 miles |
| 10 B. W. G. iron | 120 miles |
| 12 B. W. G. iron | 90 miles |
| 16 B. & S. cable, copper | 40 miles |
| 19 B. & S. cable, copper | 30 miles |
| 22 B. & S. cable, copper | 20 miles |
+-----------------------------+----------------------+

In 1893, Oliver Heaviside proposed that the inductance of telephone
lines be increased above the amount natural for the inter-axial
spacing, with a view to counteracting the hurtful effects of the
capacity. His meaning was that the increased inductance--a harmful
quality in a circuit not having also a harmfully great capacity--would
act oppositely to the capacity, and if properly chosen and applied,
should decrease or eliminate distortion by making the line's effect on
fundamentals and harmonics more nearly uniform, and as well should
reduce the attenuation by neutralizing the action of the capacity in
dissipating energy.

There are two ways in which inductance might be introduced into a
telephone line. As the capacity whose effects are to be neutralized
is distributed unif