How could one lighthouse be distinguished from another?
Years ago, to help the sailor determine his location, the Lighthouse Board (which was in charge of lighthouses from 1852–1910) issued an order to have each lighthouse painted in different colors and/or designs. But what about night? You can’t see colors or patterns at night, but you can see lights. However, unless there was some way to make each light different you could have the same problem. Early on, they built multiple lights (that is, two or three together.) This was one way to help the sailors at sea determine their location, but it was very expensive. Mounting a group of lights on a rotating framework made it possible to produce a special pattern of light for each lighthouse. The rotating lights made a lighthouse look like it was flashing its light on and off. The invention of the Fresnel (pronounced “Frey Nel”) lens in 1822 was probably the most important discovery in lighting technology. As well as enabling man to produce an unlimited number of flashing combinations, it also i
