For most of their history, lighthouses (celebrated nationally every Aug. 7) were not houses.

At the very beginning, they weren’t even buildings.

Nature periodically provided the first nighttime navigational landmarks in the form of glowing volcanoes.

The first man-made lighthouse was the tallest ever built. The Pharos of Alexandria, Egypt, a 450-foot tower completed about 280 B.C., used an open fire at its apex as the light source.

The tower lasted 1,500 years until it was destroyed by an earthquake in the 14th century.

The modern era of lighthouses began in the early 1700s, with a proliferation of the structures made necessary by burgeoning transatlantic commerce.

Early lighthouses were illuminated by wood or burning coal, then candles, then lanterns fueled with whale or vegetable oil, then electric lighting.

In 1782 Swiss scientist Aime Argand invented a lamp which provided the standard technology for lighting for more than a century. The Argand lamp was replaced in 1901 by the safer, cleaner Dalen light, which became the predominant light source until lighthouses went electric in the 1960s.

First used in 1823, the pivotal technology for the lamp was the Fresnel lens, a lightweight multi-sectioned glass lens capable of capturing 85 percent of the source’s illumination and focusing it with four times the brightness of any previous reflectors (think theater stage lights).

Rotating mechanisms were added to give the light a blinking pattern. Each lighthouse used a distinguishing on-and-off signature (sometimes in different colors) to avoid confusion.

You may have heard of this debunked conversation off the coast of Newfoundland:

Americans: “Please divert your course 15 degrees to the north to avoid a collision.”

Canadians: “Recommend you divert your course 15 degrees to the south to avoid a collision.”

Americans: “This is the aircraft carrier USS Lincoln, the second largest ship in the United States’ Atlantic fleet. We are accompanied by three destroyers, three cruisers and numerous support vessels. I demand that you change your course 15 degrees north or countermeasures will be undertaken to ensure the safety of this ship.”

Canadians: “This is a lighthouse. Your call.”

[mlw_quizmaster quiz=12]