The fourth order Fresnel lens is an optic beauty, sophisticated and precise. What makes a fourth order so unique? It’s symphony of refracted light.

French inventor Augustin Fresnel set out to design a lighthouse optic that would save lives, a navigational aid for mariners to follow. What he managed to create was a jewel-like devise that would capture the imagination of lighthouse lovers worldwide.

The Fresnel lens was developed in several “orders” from the immense (Hyperdial and Meso-Radial), to small (6th Order), with many sizes in between (1st, 2nd, 3rd, 3˝, 4th, 5th). The fourth order lenses were designed to service harbor and river lights, marking entrances and guiding ships around dangerous outcroppings. 

Not all fourth order lenses were created exactly alike. Their universal purpose was to create a focal length of 375mm. Some of the fourth order optics have several “bull’s eyes”, circular shaped panes of glass that reflect their light through a round center, or “eye”. This beauty has twelve precisely placed bull’s eyes positioned around the lens’ circumference, making it an intricate example of glass-forming genius. 

The Henri La Paute Company of Paris, a company with origins as the French royal clock makers, made this revolving lens using their extensive knowledge to create the clockwork mechanism. With the intricate glasswork and cast bronze frame, this is an extremely heavy optic, yet is almost delicate in appearance.

Not unlike other Fresnel lenses that were removed from lighthouses, this forgotten treasure was discovered in a secured warehouse. As some beacons were automated and upgraded with modern optics, the Fresnel lenses were sent to storage for safekeeping. With the renewed interest in lighthouse history and lore, the U.S. Coast Guard has been uncovering these maritime gems, restoring them and placing them on display. 

Researchers are combing through historic records, warehouse manifests and lightkeepers correspondences to find the origin of this particular lens. Its “story” is yet to be discovered. In fact, if you just happen to have information regarding this lens and know which lighthouse it came from, you could play a big part in preserving maritime history! Curators will not rest until the origins are found and the full story is revealed.

The fourth order Fresnel lens on display in Yorktown, Virginia, resides in the Canfield Hall Atrium located in the National Aids to Navigation School, USCG Reserve Training Center. Within the atrium, lighthouse optics in every size (including other fourth order lenses), with different clockwork mechanisms are on display.