Southeast Light is a lighthouse located on Mohegan Bluffs at the southeastern corner of Block Island, Rhode Island. It was designated a US National Historic Landmark in 1997. Although Congress appropriated $9,000 to build this light in 1856, the funds were used to build a new Block Island North Light after the old one was washed away in a storm. The light was finally built in 1875. The original optic was a first order Fresnel lens standing about 12 feet tall with four circular wicks burning whale oil. The whale oil was replaced by kerosene in 1880 and the lens was modified to rotate floating in a pool of mercury, driven by a clock whose weights had to be rewound every four hours. In 1990, the Coast Guard deactivated the light and replaced it with a nearby steel tower. Because of ongoing erosion of the bluffs, in 1993 the entire 2,000 ton structure was moved about 300 feet back from the cliffs. After the move, the Coast Guard decided not to reinstall the mercury float lens, but instead installed the first order lens from the Cape Lookout Lighthouse. The lighthouse has a museum displaying the original Fresnel lens. The museum is open during the summer season provides tours of the light tower, and has a small gift shop.