What happens in fog when the light isn visible?
In situations like this there is another method of notifying the mariner, using sound. It is called a foghorn. The first one was used in 1719 at Boston light and it was, of all things, a cannon. Can you imagine being a lighthouse keeper and having to fire the cannon every hour when there was fog? During a long spell of fog you wouldn’t get any sleep. Later they tried various other means of making a noise for warning. Fog bells were used as well as steam whistles and reed trumpets and sirens. The sounds they gave out were generally low-pitched and very mournful—almost like a wail. Each one emitted a specific number of blasts every minute so it could be told apart from all others. Today, an automatic sensor, which detects moisture in the air, turns on the fog signals when needed. There are also soundless fog signals called radio beacons (an electronic device). These fog signals were not placed everywhere. Although some places experience no fog problems, fog-warning devices are very neces
