| Size of wire B. & S. gauge | Tensile strength, lbs. | Size of wire B. & S. gauge | Tensile strength, lbs. |
|---|---|---|---|
| 0000 | 9971 | 9 | 617 |
| 000 | 7907 | 10 | 489 |
| 00 | 6271 | 11 | 388 |
| 0 | 4973 | 12 | 307 |
| 1 | 3943 | 13 | 244 |
| 2 | 3127 | 14 | 193 |
| 3 | 2480 | 15 | 153 |
| 4 | 1967 | 16 | 133 |
| 5 | 1559 | 17 | 97 |
| 6 | 1237 | 18 | 77 |
| 7 | 980 | 19 | 161 |
| 8 | 778 | 20 | 48 |
Pole Lines.—In the majority of cases overhead conductors are supported by wooden poles. In tropical countries, however, such as India, Central America, etc., where wood is rapidly destroyed by the ravages of white ants and other insects, iron poles are almost exclusively used for telegraph, telephone, and other electric transmission lines. The form of iron pole generally adopted consists of tapering shells of sheet iron of convenient length, riveted together at their ends and set into cast iron base plates which are buried in the ground.
