The History and Use of Metal Detectors

The History and Use of Metal Detectors In 1881, Alexander Graham Bell invented the first metal detector. As President James Garfield lay dying of an assassins bullet, Bell hurriedly invented a crude metal detector in an unsuccessful attempt to locate the fatal slug. Bells metal detector was an electromagnetic device he called the induction balance. Gerhard Fischar In 1925, Gerhard Fischar invented a portable metal detector. Fischars model was first sold commercially in 1931 and Fischar was behind the first large-scale production of metal detectors. According to the experts at AS Company: In the late 1920s, Dr. Gerhard Fisher, the founder of Fisher Research Laboratory, was commissioned as a research engineer with the Federal Telegraph Co. and Western Air Express to develop airborne direction finding equipment. He was awarded some of the first patents issued in the field of airborne direction finding by means of radio. In the course of his work, he encountered some strange errors and once he solved these problems, he had the foresight to apply the solution to a completely unrelated field, that of metal and mineral detection. Other Uses Simply put, a metal detector  is an  electronic instrument  which detects the presence of  metal  nearby. Metal detectors can help people find metal inclusions hidden within objects, or metal objects buried underground. Metal detectors often consist of a handheld unit with a sensor probe which the user can sweep over the ground or other objects. If the sensor comes near a piece of metal, the user will hear a tone, or see a needle move on an indicator. Usually, the device gives some indication of distance; the closer the metal is, the higher the tone or the higher the needle goes. Another common type is the stationary walk through metal detector which is used for  security screening  at access points in prisons, courthouses, and airports to detect concealed metal weapons on a persons body. The simplest form of a metal detector consists of an  oscillator  producing an alternating current that passes through a coil producing an alternating  magnetic field. If a piece of electrically conductive metal is close to the coil,  eddy currents  will be induced in the metal, and this produces a magnetic field of its own. If another coil is used to measure the magnetic field (acting as a  magnetometer), the change in the magnetic field due to the metallic object can be detected. The first industrial metal detectors were developed in the 1960s and were used extensively for mineral prospecting and other industrial applications. Uses include  de-mining  (the detection of  land mines), the detection of weapons such as knives and guns (especially in  airport security),  geophysical prospecting,  archaeology,  and  treasure hunting. Metal detectors are also used to detect foreign bodies in food as well as in the  construction industry  to detect  steel reinforcing bars  in concrete and pipes plus wires buried in walls or floors.

5 Classic and Heartbreaking Slave Narratives

5 Classic and Heartbreaking Slave Narratives Slave narratives became an important form of literary expression before the Civil War, when about 65 memoirs by former slaves were published as books or pamphlets. The stories told by former slaves helped to stir public opinion against slavery. The Most Interesting Slave Narratives The prominent abolitionist Frederick Douglass first gained widespread public attention with the publication of his own classic slave narrative in the 1840s. His book and others provided vivid firsthand testimony about life as a slave. A slave narrative published in the early 1850s by Solomon Northup, a free black New York resident who was kidnapped into slavery, aroused outrage. Northups story has become widely known from the Oscar-winning film, 12 Years a Slave,  based on his searing account of life under the cruel slave system of Louisiana plantations. In the years following the Civil War, about 55 full-length slave narratives were published. Remarkably, two more recently-discovered slave narratives were published in November 2007. The authors listed wrote some of the most important and widely-read slave narratives. Olaudah Equiano The first noteworthy slave narrative was The Interesting Narrative of the Life of O. Equiano, or G. Vassa, the African, which was published in London in the late 1780s. The book’s author, Olaudah Equiano, had been born in present-day Nigeria in the 1740s. He was taken into slavery when he was about 11 years old. After being transported to Virginia, he was purchased by an English naval officer, given the name Gustavus Vassa, and offered the opportunity to educate himself while serving as a servant aboard ship. He was later sold to a Quaker merchant and given a chance to trade and earn his own freedom. After buying his freedom, he traveled to London, where he settled and became involved with groups seeking the abolition of the slave trade. Equiano’s book was notable because he could write about his pre-slavery childhood in West Africa, and he described the horrors of the slave trade from the perspective of one of its victims. The arguments Equiano made in his book against the slave trade were used by British reformers who eventually succeeded in ending it. Frederick Douglass The best-known and most influential book by an escaped slave was The Narrative of the Life of Frederick Douglass, an American Slave, which was first published in 1845. Douglass had been born into slavery in 1818 on the eastern shore of Maryland, and after successfully escaping in 1838, settled in New Bedford, Massachusetts. By the early 1840s, Douglass had come into contact with the Massachusetts Anti-Slavery Society and became a lecturer, educating audiences about slavery. It’s believed that Douglass wrote his autobiography partly to counter skeptics who believed he must be exaggerating details of his life. The book, featuring introductions by abolitionist leaders William Lloyd Garrison and Wendell Phillips, became a sensation. It made Douglass famous, and he went on to be one of the greatest leaders of the American abolition movement. Indeed, the sudden fame was seen as a danger. Douglass traveled to the British Isles on a speaking tour in the late 1840s, partly to escape the threat of being apprehended as a fugitive slave. A decade later, the book would be enlarged as My Bondage And My Freedom. In the early 1880s, Douglass would publish an even larger autobiography, The Life and Times of Frederick Douglass, Written by Himself. Harriet Jacobs Born into slavery in North Carolina in 1813, Harriet Jacobs was taught to read and write by the woman who owned her. But when her owner died, young Jacobs was left to a relative who treated her far worse. When she was a teenager, her master made sexual advances on her. Finally, one night in 1835, she attempted to escape. The runaway didn’t get far and wound up hiding in a small attic space above the house of her grandmother, who had been set free by her master some years earlier. Incredibly, Jacobs spent seven years in hiding, and health problems caused by her constant confinement led her family to find a sea captain who would smuggle her north. Jacobs found a job as a domestic servant in New York, but life in freedom was not without dangers. There was a fear that slave catchers, empowered by the Fugitive Slave Law, might track her down. She eventually moved on to Massachusetts. In 1862, under the pen name Linda Brent, she published her memoir Incidents in the Live of a Slave Girl, Written by Herself. William Wells Brown Born into slavery in Kentucky in 1815, William Wells Brown had several masters before reaching adulthood. When he was 19, his owner made the mistake of taking him to Cincinnati in the free state of Ohio. Brown ran off and made his way to Dayton. Here, a Quaker who did not believe in slavery helped him and gave him a place to stay. By the late 1830s, he was active in the abolitionist movement and was living in Buffalo, New York. Here, his house became a station on the Underground Railroad. Brown eventually moved to Massachusetts. When he wrote a memoir, Narrative of William W. Brown, a Fugitive Slave, Written by Himself, it was published by the Boston Anti-Slavery Office in 1847. The book was very popular and went through four editions in the United States. It was also published in several British editions. He traveled to England to lecture. When the Fugitive Slave Law was passed in the U.S., he chose to remain in Europe for several years, rather than risk being recaptured. While in London, Brown wrote a novel, Clotel; or the President’s Daughter. The book played upon the idea, then-current in the U.S., that Thomas Jefferson fathered a mulatto daughter who had been sold at a slave auction. After returning to America, Brown continued his abolitionist activities, and along with Frederick Douglass, helped recruit black soldiers into the Union Army during the Civil War. His desire for education continued, and he became a practicing physician in his later years. Slave Narratives from the Federal Writers Project In the late 1930s, as part of the Works Project Administration, field workers from the Federal Writers Project endeavored to interview elderly Americans who had lived as slaves. More than 2,300 people provided recollections, which were transcribed and preserved as typescripts. The Library of Congress hosts Born in Slavery, an online exhibit of the interviews. They are generally fairly short, and the accuracy of some of the material can be questioned, as the interviewees were recalling events from more than 70 years earlier. But some of the interviews are quite remarkable. The introduction to the collection is a good place to start exploring. Sources Born in Slavery: Slave Narratives from the Federal Writers Project. Library of Congress, 1936 to 1938. Brown, William Wells. Clotel; or, The Presidents Daughter: A Narrative of Slave Life in the United States. Electronic Edition, University Library, UNC-Chapel Hill, University of North Carolina at Chapel Hill, 2004. Brown, William Wells. Narrative of William W. Brown, A Fugitive Slave. Written by Himself. Electronic Edition, Academic Affairs Library, UNC-CH, University of North Carolina at Chapel Hill, 2001. Douglass, Frederick. Life and Times of Frederick Douglass. Wilder Publications, January 22, 2008. Douglass, Frederick. My Bondage and My Freedom. Kindle Edition. Digireads.com, April 3, 2004. Douglass, Frederick. The Capital and the Bay: Narratives of Washington and the Chesapeake Bay Region. The Library of Congress, 1849. Jacobs, Harriet. Incidents in the Life of a Slave Girl. Paperback, CreateSpace Independent Publishing Platform, November 1, 2018.