Site hosted by Angelfire.com: Build your free website today!
pt arena Lights of the Coast  
history technology lights resources culture

Creating the Lights ...from bonfires to lenses

Developed by Augustin Fresnel of France and introduced in 1822, the Fresnel lens signaled the arrival of the golden age of lighthouses. Through a sophisticated arrangement of prisms, the Fresnel lens focuses light into a concentrated beam that, in some cases, could be seen from more than 20 miles away. Designed in a series of seven sizes (called orders, 1st through 6th, with a three-and-a-half order), the Fresnel lens could accommodate a variety of lighthouse sizes and functions. A sixth-order lens was the smallest in size and therefore had the smallest focal distance, while a first-order lens was the largest and, in some cases, reached a height of up to 12 feet. Though he died only five years after inventing the lens, Augustin Fresnel's contribution to the lighthouse was, and still is, utilized to a great extent. From wood fires and candles to oil lamps and incandescent bulbs, no technological advance contributed more significantly to lighthouses than the Fresnel lens.

 © 2001, Lights of the Coast Wednesday, November 19, 2003