The Flashlight

The Flashlight. Presque Isle Lighthouse. , In the early 19th Century the Great Lakes provided the single most important transportation system in the country. Throughout the lakes, mariners depended heavily on lighthouses to warn of hazards to navigation and to mark major land features. , A fourth order “Fresnel” (freh-nel) lens, designed by French physicist Augustin Fresnel, was mounted at the top of the tower. Encased in brass, a single oil lamp projected a warning beam visible at up to 13 nautical miles away. Because each light had a characteristic signal, mariners watched for two red and four white flashes, informing them that they were indeed seeing the Presque Isle light or “flashlight,” as it was commonly known. , Responsibility for maintaining the light rests with the U.S. Coast Guard. Modern day shipboard electronics have greatly reduced the need for lighthouses, although they remain a significant geographic point of reference for small boats. , Throughout the Great Lakes early ship masters depended heavily on lighthouses as a fundamental aide to navigation. More than 100 lighthouses were scattered from Lake Superior east to the headwaters of the St. Lawrence. , The keeper was a slave to the light and had to climb the tower at least every 4 hours each night to check the oil supply, clean the lens, and reset the lens rotating mechanism. , The lighthouse was electrified in the 1920’s and today the light is cast by a 250 watt bulb inside a 300mm plastic lens. It displays a fixed white light on a three-second on, three-second off sequence. The “keeper” of today is an electronic light sensor.