LIGHTS & THE FRESNEL LENS

These postage stamps show the different lights used over nearly three

centuries by the Alderney lighthouse and are typical of many other

lighthouses. From the left:

1725 coal fire

1779 oil lantern

1790 Argand lamp

(Oil lamp with tank and tin cylinder over the flames)

1818 a revolving apparatus

1952 electrification

While this Danish stamp of 1960 illustrates a 16th

century “swinging fire

which was hoisted to high level by a lever arm. In England the device was

called a swape.

Augustin-Jean Fresnel 1788-1827

Fresnel was a French physicist who made significant contributions to the

theory of wave optics. He invented the Fresnel lens which was widely

adopted for use in lighthouses. In 1819 he became Commissioner of

Lighthouses. In 1823 he was elected a member of the Academie des

Sciences in Paris. In 1825 he became a member of the Royal Society of

London and in 1827 they awarded him the Rumford Medal. Fresnel died of

tuberculosis at the age of 39.

The idea of a thin light lens in separate sections is often attributed to Georges-

Louis Leclerc, Comte de Buffon.

(Lighthouses, F Ross Holland, 1995)

An oil lamp and Fresnel lens combination

The Fresnel lens (terrypepper.com)

Example of six orders of Fresnel lenses (michiganlights.com)

A first order Fresnel lens originally used at Cape Canaveral

2nd order Fresnel lens

By comparison, a 6th

order Fresnel lens

A Fresnel lens and light source

The electric light at the South Foreland lighthouse was provided by a

steam-driven magneto-electric generator (The Graphic, 3 February 1872).

The generator was developed by Professor Frederick Hale Holmes.

The first electrically lit light was at the South Foreland lighthouse in

December 1858. The candle-power was over 1500 and the light source was of

manageable size for optic control of the beam. It was only an experimental

installation and it was not until 6th

June 1862 that the apparatus was in

service in its final form. In France, M. Reynaud was responsible for the arc-

lights at La Heve in the last days of 1863. They were a combination of the

Serrin Arc lamp and the magneto-electric machines of Nollet. The French

light was steadier than that of Holmes and many of its features, including the

use of alternating current, were adopted in later British installations.

(Lighthouses, Patrick Beaver, 1971)

Exhibit of the US Lighthouse Board at the Chicago’s World Fair, 1892-93,

included (on the right) a 1st Order Fresnel lens (Holland)