SYNCHRONOUS SIGNALLING IN NAVIGATION (CLASSIC REPRINT)

Excerpt from Synchronous Signalling in NavigationSynchronised signalling is based on a fact, the ascertainment of which is old in the history of scientific advance that disturbances travel with different speeds in different media. Light and other electro-magnetic disturbances (such as telegraphy or wireless may be regarded as instantaneously propagated, sound travels relatively slowly, and in water more than four times as fast as in air. These are fundamental facts which have been made the subject of accurate measurements and certainly require no further experiments to establish. They are the scientific bases of synchronous signalling. The practical basis differs somewhat accord ing as we consider its application to coastal stations, or to the prevention of collision. Re garding the first, we may say that two factors only are involved