In 1893, the French Government displayed this second-order bivalve Fresnel lens at the World’s Fair in Chicago. The Fair was a place where many countries showcased their recent scientific advancements and inventions. The lens is sitting on a cast-iron pedestal. Within the pedestal are the drum, gears, and mechanisms that turned the lens. A plaque below the lens stated “This apparatus, the greatest ever made according to the new principals of lighting lights, has been drawn and executed with the agreement of the French Lighthouse Board … Paris 1893.” Because the lens weighed close to seven tons, the French government decided to sell it rather than ship it back to France. In 1898, the U.S. Lighthouse Board purchased the lens and installed it in the south tower at Navesink Lighthouse. A power house was built behind the lighthouses to generate electricity for the light.
In 1917, the lighthouse service replaced the electric light with an incandescent oil vapor lamp. The new lamp was similar to lanterns used today by campers and was less expensive for the lighthouse service to maintain and operate. Less than 10 years later commercial electric power became available in the area surrounding the lighthouse. The oil vapor lamp was removed and three light bulbs were installed inside the lens. Through all these changes, the 1893 lens shown in the photo stayed in use at the top of the tower. By 1949 the lighthouse was no longer needed. A few years later the lens was removed and put on display at the Boston Museum of Science. Later, funds were raised in Highlands to bring the lens back to Navesink. Today, it is displayed in the same building that originally generated the electricity to light the lens.
1. Why do you think the French government displayed the Fresnel lens at the Chicago World’s Fair?
2. What was different about this Fresnel lens? How did it improve upon earlier lenses? (Refer to Reading 2, if necessary.)
3. Look carefully at the photo. How many circular facets are there in the central bull’s-eye? How many panels surround the bull’s-eye?
4. Look at the pedestal. Can you identify the drum and gears that turned the lens?
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