---------+-----------+-----------+----------+---------+------------+----------+
| 31 | 8.928 | 79.70 | 538.4 | 0.1299 | 4,145. | 7.698 | 0.0002413 |0.001857 |
| 32 | 7.950 | 63.21 | 856.2 | 0.1638 | 5,227. | 6.105 | 0.0001913 |0.001168 |
| 33 | 7.080 | 50.13 | 1,361. | 0.2066 | 6,591. | 4.841 | 0.0001517 |0.0007346 |
| 34 | 6.305 | 39.75 | 2,165. | 0.2605 | 8,311. | 3.839 | 0.0001203 |0.0004620 |
| 35 | 5.615 | 31.52 | 3,441. | 0.3284 | 10,480. | 3.045 | 0.00009543 |0.0002905 |
| 36 | 5.0 | 25.0 | 5,473. | 0.4142 | 13,210. | 2.414 | 0.00007568 |0.0001827 |
| 37 | 4.453 | 19.83 | 8,702. | 0.5222 | 16,660. | 1.915 | 0.00006001 |0.0001149 |
| 38 | 3.965 | 15.72 | 13,870. | 0.6585 | 21,010. | 1.519 | 0.00004759 |0.00007210|
| 39 | 3.531 | 12.47 | 22,000. | 0.8304 | 26,500. | 1.204 | 0.00003774 |0.00004545|
| 40 | 3.145 | 9.888 | 34,980. | 1.047 | 33,410. | 0.9550 | 0.00002993 |0.00002858|
+-------+----------+----------+-----------+-----------+----------+---------+------------+----------+

[Illustration: SOUTH OFFICE OF HOME TELEPHONE COMPANY, SAN FRANCISCO]

In the Brown and Sharpe gauge the sizes, beginning with the largest,
are numbered 0000, 000, 00, 0, 1, 2, and so on up to 40. Sizes larger
than about No. 16 B.&S. gauge are seldom used as magnet wire in
telephony, but for the purpose of making the list complete, Table III
is given, including all of the sizes of the B.&S. gauge.

In Table III there is given for each gauge number the diameter of the
wire in mils (thousandths of an inch); the cross-sectional area in
circular mils (a unit area equal to that of a circle having a diameter
of one one-thousandth of an inch); the resistance of the wire in
various units of length and weight; the length of the wire in terms of
resistance and of weight; and the weight of the wire in terms of its
length and resistance.

It is to be understood that in Table III the wire referred to is bare
wire and is of pure copper. It is not commercially practicable to use
absolutely pure copper, and the ordinary magnet wire has a
conductivity equal to about 98 per cent of that of pure copper. The
figures given in this table are sufficiently accurate for all ordinary
practical purposes.

_Silk and Cotton Insulation_. The insulating material usually employed
fo