Heavy Lights at America's Oldest Lighthouse

Boston Light, America's oldest lighthouse station, turned 300 this year. Built on a small, rocky island near the entrance to Boston Harbor, it draws visitors not only for its age, but for the chance it offers to view a piece of technology that some argue changed the course of the 19th century: a massive lens made from hundreds of sparkling glass prisms. Sally Snowman, keeper of Boston Light, with the lighthouse's1859 Fresnel lens.Image Credit:Petty Officer 3rd class Andrew Baressi "It's 4,000 po...