1911 Encyclopædia Britannica/Beaufort Scale
BEAUFORT SCALE, a series of numbers from 0 to 12 arranged by Admiral Sir Francis Beaufort (1774–1857) in 1805, to indicate the strength of the wind from a calm, force 0, to a hurricane, force 12, with sailing directions such as “5, smacks shorten sails” for coast purposes, and “royals, &c., ‘full and by’ ” for the open sea. An exhaustive report was made in 1906 by the Meteorological Office on the relation between the estimates of wind-force according to Beaufort’s scale and the velocities recorded by anemometers belonging to the office, from which the following table is taken:—
| Beaufort scale. | Corresponding wind. | Limits of hourly velocity. |
| Numbers. | Miles per hour. | |
| 0 | Calm | Under 2 |
| 1–3 | Light breeze | 2–12 |
| 4–5 | Moderate wind | 13–23 |
| 6–7 | Strong wind | 24–37 |
| 8–9 | Gale | 38–55 |
| 10–11 | Storm | 56–75 |
| 12 | Hurricane | Above 75 |