THE SEMAPHORE.
If signal stations are to be permanently occupied, and it is impracticable to electrically connect them, communication may be facilitated by erecting semaphores.
Semaphores, while primarily used for day signaling, can be advantageously used at night by attaching lights to the arms.
The navy semaphore consists of four arms pivoted at the ends, three on one side of the upright, or pole, and one on the other side. These arms have three positions: Horizontal; upward at an angle of 45° to the horizontal; downward at an angle of 45° to the horizontal.
Full instructions for the operation of the semaphore, and also for the use of balls, cones, drums, pennants, and whefts as distant signals, are given in the International Code of Signals.