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Technology:

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.