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Keweenaw Waterway Lower Entrance Light
The Keweenaw Waterway Lower Entrance Light, also known as the Portage Entry Light, is a lighthouse located at the south end of breakwater at mouth of the Portage River in Torch Lake Township. It was listed on the National Register of Historic Places in 2014. History The Portage River was first dredged in 1860, and the need for a light to mark the mouth of the waterway was quickly obvious. In 1866, Congress appropriated $7500 to construct range lights at this location, which were constructed in 1868. The Federal government purchased the Keweenaw Waterway in 1891, after which the United States Army Corps of Engineers began a program to improve navigation in the waterway. By 1898, a breakwater and a western pier extending offshore was erected here. In 1902 a wooden frame tower erected at the end of the pier to house a light. This proved inadequate, and it was replaced with an iron tower in 1911. In 1913, work began on a new harbor inside the waterway, and in 1917 Congress appropr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torch Lake Township, Houghton County, Michigan
Torch Lake Township is a civil township of Houghton County in the U.S. state of Michigan. As of the 2010 census, the population of the township was 1,880. The township was established in 1886 and is one of the largest townships in Houghton County by area. It is surrounded by the Torch Lake, the Portage Lake, and Lake Superior. As well as a large number of unincorporated communities, the township also includes a portion of the Baraga State Forest which lies along the shores of Keweenaw Bay. The township borders Schoolcraft Township to the north, Osceola Township to the northwest, and Chassell Township to the southwest. The community of Hubbell serves as the major population center of the township, as well as hosting the Township Hall itself. The mostly uninhabited 91-acre Rabbit Island, located offshore in Lake Superior, is a part of the township. Communities *Bootjack is an unincorporated community in the township, it borders the settlement called Dreamland and sits on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fresnel Lens
A Fresnel lens ( ; ; or ) is a type of composite compact lens developed by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses. It has been called "the invention that saved a million ships." The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. The simpler dioptric (purely refractive) form of the lens was first proposed by Count Buffon and independently reinvented by Fresnel. The ''catadioptric'' form of the lens, entirely invented by Fresnel, has outer elements that use total internal reflection as well as refraction; it can capture more oblique light from a light source and add it to the beam of a lighthouse, making the light visible from greater distances. Description The Fresnel lens redu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
