A tower used as an aid to navigation marking a hazard or point of entrance Usually consisting of a very bright light atop a tower and often a foghorn or siren and radio beacon
Added in 1820s to aid navigation for vessels using the deep water channels It is still in use today and plays a central role in the navigational system for ships entering Portsmouth Harbour
A lighthouse is a tower containing a powerful flashing lamp that is built on the coast or on a small island. Lighthouses are used to guide ships or to warn them of danger. Structure, usually with a tower, built onshore or on the seabed to signal danger or provide aid to seafarers. The first known lighthouse was the Pharos of Alexandria. The modern lighthouse dates only from the early 18th century. Initially made of wood, these towers were often washed away in severe storms. The first lighthouse made of interlocking masonry blocks was built on the treacherous Eddystone Rocks reef, off Plymouth, England (1759). Interlocking masonry blocks remained the principal material of lighthouse construction until they were replaced by concrete and steel in the 20th century. Modern construction methods have facilitated the building of offshore lighthouses. The most common illuminant is the electric-filament lamp. Refinements in lenses (e.g., the Fresnel lens) and reflectors made it possible to substantially increase the light's intensity. Radio and satellite-based navigation systems have greatly reduced the need for large lighthouses in sighting land
A tower or other building with a powerful light at top, erected at the entrance of a port, or at some important point on a coast, to serve as a guide to mariners at night; a pharos