Lighthouse

Lighthouse. . , This lighthouse was built after a 1905 storm damaged 29 boats and resulted in more than three million dollars in damages. , Split Rock Lighthouse stands as a beacon to safety in the lake shipping industry. Construction began in 1909, with a $75,000 budget. Duluth firm L. D. Campbell and Son built the lighthouse, with up to 30 men working on the grounds at any one time. On July 31, 1910, Split Rock Lighthouse was lit for the first time by Orren "Pete" Young., What Makes the Light? , There is a lens room high within the lighthouse. Within the room, a Third Order Fresnel bivalve lens revolves. The brass-framed lens is made up of 252 prisms., A clockwork gear and weight system makes the lens rotate, which floats on a bed of mercury. As a 200-pound weight descends through a pipe in the center of the tower, a cable connected to it unspools, causing a series of gears to spin. This process, triggered by hand, must be repeated every two hours. The keeper and his assistants alternated night watches to ensure uninterrupted rotations every night of the shipping season. The beacon has a range of 22 miles. It spans Lake Superior, almost reaching the Bayfield Peninsula., Split Rock Lighthouse is a bearing light station, navigators use it to "find their bearings," or location. Every lighthouse has a unique flashing pattern and/or color, known as a "characteristic." Split Rock's characteristic was one flash of white light, made by a kerosene lantern, every 10 seconds throughout the night. During the day, when the beacon was not lit, the lighthouse still helped navigators find their bearings. Split Rock's distinctive yellow brick and its black top were its day-markers., Top: Lighthouse During Construction, circa 1909. , Bottom: Lens assembly with kerosene lamp, circa 1920. MNHS collections.