Yarmouth, Nova Scotia, Canada

The Fresnel Lens, or Cape Forchu Light

In 1838, the Commissioners for Lighthouses approved a grant to build a light at Cape Forchu at the mouth of Yarmouth Harbour. In 1839, the first lighthouse in Yarmouth was erected, and the Yarmouth Herald reported in October that the lantern and apparatus for the light had arrived onboard the Schooner Surprise. Lt. James Fox, formerly of the Royal Navy, was the first lighthouse keeper at Cape Forchu. Sadly, he only held the position for three months. Upon his passing away, his son John took over the job of lighthouse keeper; a position he would hold for 33 years.

There would be no major changes to the lighthouse until 1908, when the lens that is now on display at the museum was installed. The new lens was a sophisticated improvement over the original. The "Fresnel" lens was named after its inventor, Augustin-Jean Fresnel (1788-1827), a French physicist and engineer who worked for the French government. He devised a method of producing circularly polarized light and promoted the replacement of mirrors by compound lenses in lighthouses.

The lens was built in Paris and cost $38,000 Canadian; it weighs approximately 3300 pounds and has 360 prisms. The lens was floated in a vat of mercury, and rotated by weights, similar to a grandfather clock. These weights had to be wound every three hours during the night, and the rotation blocked in the morning by bolts inserted in the mechanism. Every night the light keeper and his assistant made six trips, three each, up a series of narrow stairways that wound to the top of the light.

In 1962, a new modern structure replaced the 122-year-old lighthouse, and the "new light" was installed to replace the Fresnel lens. Today, the Cape Forchu light station is a tourist attraction, accessible by road along a scenic route that offers views of both Yarmouth Harbour and the ocean. For more on the Cape Forchu light station, there is a booklet at the base of the light, and additional information on Cape Forchu in our archives.

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