Aethra was the name given to the 132nd asteroid discovered. It was discovered by Watson at Ann Arbor on June the 13th 1873. The asteroid was named after Aethra, mother of Theseus from Greek legend.
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Althaea was the name given to the 119th asteroid discovered. It was discovered by Watson at Ann Arbor, Michigan, on April the 3rd, 1872, the eleventh, and last, of the small planets detected by him.
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Arbor Day was a day set apart by most of the States and Territories of the USA for the planting of trees. Arbor Day was inaugurated by the Nebraska State Board of Agriculture in 1874. Arbor Day was held on the second Wednesday of April.
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In horology, a roller table is a flat disk on the arbor of the balance of a watch, holding the jewel which rolls in and out of the fork at the end of the lever of the escapement.
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A watch is a portable timepiece formerly carried in the pocket, now commonly worn upon band around the wrist. The watch was invented at Nurnberg in the end of^he 15th century.
In early mechanical pocket watches, the wheels are urged on by the force of a spiral spring, generally of steel, contained in a cylindrical barrel or box, to which one end of a chain is fixed, the chain also making several turns round the barrel outside; the other end of the chain is fixed to the bottom of a cone with a spiral groove cut on it, known as the fusee. On the bottom of the fusee the first or great wheel is put. The barrel-arbor is so fixed in the frame that it cannot turn when the fusee is winding up. The inner end of the spring hooks on to the barrel-arbor, the outer to the inside of the barrel. If the fusee iy turned round in the proper direction it will take on the chain, and consequently take it off from the barrel. This coils up the spring; and if the fusee and great wheel are left to themselves, the force exerted by the spring in the barrel to unroll itself will make the barrel turn in a contrary direction to that by which it was bent up. This force communicating itself to the wheels will set them in motion. Their time of continuing in motion will depend on the number of turns of the spiral groove on the fusee, the number of teeth in the first or great wheel, and on the number of leaves in the pinion upon which the great wheel acts, etc.
The necessity of keeping the watch from 'running down', and of making the wheels move with uniform motion, gave rise to the use of the balance-wheel and hair-spring (taking the place of the pendulum of a clock) and the variously and ingeniously designed mechanism, the escapement. On the perfection of the escapement the time-keeping qualities of a watch largely depend. Of the many varieties invented and perfected, by the 20th century watches were almost exclusively provided with either the horizontal, the lever, or the chronometer or detached escapement. In all but the best class English watches the fusee had been abandoned in favour of the going-barrel. The latter offers better facilities for keyless work, and keyless watches were manufactured in increasing quantities. The going-barrel watch could also be produced at a cheaper rate, and for ordinary purposes was amply reliable.
The main-spring in this class of watch is very long, but only a few coils are brought into action. The great wheel is attached to the going-barrel itself, thus the spring force is directly transmitted to the escapement. The invention of the spiral hair-spring by Dr. Hooke (about 1658), the scientific application of its properties since, and the intelligent use of compensation in the balance, combined to give to the best chronometers a very high uniformity of rate which it was impossible to excel before the invention of electronics.
A number of watches for special performances were also constructed. Such are the calendar watch, the repeater, the chronograph, etc. Large quantities of the cheaper class of watches were later made by machinery in Switzerland, France, Germany, England, and the USA. They were generally produced on the interchangeable system, that is, if any part of a watch became unfit for service, it could be cheaply replaced by an exact duplicate; the labour of the watch-repairer thus became easy and expeditious.
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Arbor Vitae is the name of several coniferous trees of the genus Thuja, allied to the cypress, with flattened branchlets, and small imbricated or scale-like leaves. The common Arbor Vitae (Thuja occidentdlis) is a native of North America, where it grows to the height of about 14 metres. The young twigs have an agreeable balsamic smell. The Chinese Arbor Vitae (Thuja orientalis), common in Britain, yields a resin which was formerly thought to have medicinal virtues.
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Nyctanthes is a genus of small Indian trees belonging to the family Oleaceae. The tree of sadness (Nyctanthes arbor-tristis) bears numerous white, salver- shaped, very fragrant flowers which open at night and fall at sunrise.
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Thuya or thuja is a genus of hardy evergreen trees belonging to the family Coniferae. They bear monoecious flowers, the male flowers being solitary, and the female in ovoid catkins. The cones are small, and of the same form as the catkins. The chief species are the North American arbor vitae, or white cedar.
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Franz Feiedrich Ernst Brunnow was a German astronomer. He was born in 1821 at Berlin. He was first assistant in the Berlin Observatory, and afterward director of the observatory at Dusseldorf and the author of a very valuable manual of spherical and practical astronomy. In 1854 he went to the USA as director of the observatory at Ann Arbor, Michigan, in which position he continued, with the exception of an intermission of one year, until 1863, when his pupil, Watson, succeeded him. In 1865 he was appointed director of the Dunsink Observatory. There he devoted himself to determinations of stellar parallax, for which, together with his Manual of Astronomy, he is principally remembered.
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Grace Lee Whitney is an American actress and singer. She was born in 1930 at Ann Arbor, Michigan. She is best known for her role as 'Yeoman Rand' in the 1960's television series 'Star Trek'.
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