A caisson lighthouse (also referred to as a sparkplug lighthouse, or bug light) is a type of
lighthouse whose superstructure rests on a
concrete
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...
or metal
caisson.
Caisson lighthouses were developed in the late nineteenth century as a cheaper alternative to
screwpile lighthouse
A screw-pile lighthouse is a lighthouse which stands on piles that are screwed into sandy or muddy sea or river bottoms. The first screw-pile lighthouse to begin construction was built by the blind Irish engineer Alexander Mitchell. Constructio ...
s. The caisson design was also more efficient as it could better withstand harsh weather, and was not as fragile. Caisson lighthouses usually have living quarters made of
cast iron
Cast iron is a class of iron– carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impur ...
, although some brick examples are known. The two American nicknames were later coined because of the structure's shape.
Gallery
See also
References
Lighthouses
Marine architecture
Caissons
{{pharology-stub