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Knight's Mechanical Encyclopedia (ed. Knight), A. (search)
rmil. — Whewell. The equinoctial armil of the Square porch of Alexandria is referred to by Hipparchus and Ptolemy. A solstitial armil is also described by Ptolemy (see Whewell, I. 201). These armding of the great wall of China; by Eratosthenes, the originator of astronomical geography; by Hipparchus, the father of mathematical astronomy; and by Ptolemy, the astronomer, A. D. 150, whose systemproducts thereof. Astrolabe. As′tro-labe. The common astrolabe (not the astrolabe of Hipparchus, used in determining the altitudes of the stars) is used for measuring angles. It is graduateBrahe's Astronomice Instauratce Mechanica gives several cuts of astrolabes. The astrolabes of Hipparchus, Ptolemy, Alhazen, and Tycho Brahe did not agree in all particulars of construction. They havsphere. The astrolabon which Martin Behaim attached to the main-mast belongs originally to Hipparchus. When Vasco de Gama landed on the east coast of Africa, he found the Indian pilots at Melind
Knight's Mechanical Encyclopedia (ed. Knight), C. (search)
amp is furnished with set screws and a peculiar pair of lips or guides. The practice of castrating calves and pigs was usual in Greece. Athenaeus, in the Deipnosophists, says : — And how much better a paunch of a castrated animal is, Hipparchus tells us : — But above all I do delight in dishes Of paunches and of tripe from gelded beasts, And love a fragrant pig within the oven. Sopater says in his Hippolytus : — But like a beauteous paunch of gelded pig, Holding within a tricted to those intended for navigators' use, on which merely the outlines of coasts, islands, etc., are represented. 2. A sheet exhibiting a statement of facts in tabular form, so arranged that any particular may be readily referred to. Hipparchus, of Alexandria (160-125 B. C.), reduced geography to a science, determining the latitude and longitude of places by celestial observations. The geography of Ptolemy was translated into Arabic by the command of the Khalif Al Maimoun, between <
Knight's Mechanical Encyclopedia (ed. Knight), D. (search)
drian Museum was visited by an august procession of philosophers during the seven centuries which separated Aristarchus from Hypatia. On the instrument, which had a plane parallel to the equator and a gnomon parallel to the earth's polar axis, Hipparchus, 150 B. C., learned the length of the year, that the four quarters of the year are not of equal length, and also observed the precession of the equinoxes. See armillary sphere. Before the time of the erection of a sun-dial in the Quirinuttee-sail. 3. An extra boat of a ship for common uses. It is clinker-built, from 12 to 14 feet long, and has a beam one third of its length. Di-op′ter. An ancient altitude, angle, and leveling instrument; said to have been invented by Hipparchus. Dioptra. Di-op′tric light. The dioptric system of lighting, used in lighthouses, as distinguished from the catoptric, which is by reflectors. Refraction instead of reflection. Lenses were used in the South Foreland light in 1752, an
Knight's Mechanical Encyclopedia (ed. Knight), L. (search)
he lowest state of the tide by three sluices. In Lincolnshire, England, 400,000 acres of feverand-ague breeding swamp-land have been transformed into fields of wheat, barley, and oats, and excellent meadows. See scoop-wheel. Lev′el. An instrument for indicating a horizontal line, or determining the position as to horizontality of an object or surface to which it is applied. See also contact-level. The Roman instruments for leveling were the libra aquaria and the dioptera of Hipparchus, the father of astronomical geography. The name is derived from libella, Lat. a balance, from the similarity in form, the long arm and perpendicular post. The word libro meant to level or to weigh. The libra aquaria, we may deduce from Vitruvius, to have been a tube with upturned ends and holding water. It was probably mounted on an axis so as to be oscillated like a balance (libra), to adjust it on a vertical plane. Vitruvius remarks that Archimedes had stated that a surface of wat
Knight's Mechanical Encyclopedia (ed. Knight), M. (search)
an have been made by the Chaldeans, by Eratosthenes, by Al Maimon, by Pire, and more lately by the French, English, Germans, and others; in Peru, Lapland, British India, and elsewhere. (See armil ; armillary-sphere ; astronomical instruments ; odometer.) We regard Eratosthenes with profound respect as the author of the science of geography, and the name thereof. The extent of each zone he determined by the length of the solstitial day, and called them elimates. The map of the world by Hipparchus (150 B. C.) is founded on the discoveries of Eratosthenes, and is the first recorded attempt to assign geographical positions by longitudes and latitudes, obtained, the former from lunar eclipses, and the latter from lengths of the shadow measured by the gnomon. In Strabo's time, about the Christian era, it was customary to draw a meridian and parallel for each important place whose position was considered as determined. Ptolemy, about A. D. 150, simplified the method, and probably int
Knight's Mechanical Encyclopedia (ed. Knight), O. (search)
egree of latitude has been made and recorded not less than fourteen times in the last 1,000 years. Its length varies in different countries, as the facts show and theory had supposed. Eratosthenes, B. C. 276, attempted the measurement of the size of the earth, by ascertaining the distance between Alexandria and Syene, the differences of latitude between which places he had found to be 1/50 of the earth's circumference. Some previous measurements are mentioned under armil (which see). Hipparchus of Nicaeea in Bithynia, 162 B. C., laid down a map by the determination of the latitude and longitude of places. A degree was measured on the shores of the Red Sea by the Khalif al Maimoun, the son of Haroun al Raschid, about A. D. 820. The exact determination of the length of a degree was considered of so much importance that, in 1735, the Academy of Sciences of Paris dispatched two commissions, one to Peru, the other to Lapland. The latter party accomplished their mission and retur
Knight's Mechanical Encyclopedia (ed. Knight), Q. (search)
ar measurements. So called from its embracing an are of 90° or somewhat more. Formerly much employed in making astronomical observations. When fixed to a wall it was called a mural quadrant; this is now superseded by the mural circle. See mural circle; mural quadrant. The quadrant appears to have been used for solar observations about 290 B. C.; and we learn that the Arabian astronomers, about 995 A. D., had a quadrant of 21 feet 8 inches and a sextant of 57 feet 9 inches radius. Hipparchus and Ptolemy used diopters, in which the distance of a star from the zenith was observed by looking through two sights fixed in a rule, annexed to a second rule, which was kept vertical by a plumb-line, the angular distance between the two rules being measured. Among the Alexandrian astronomers it was noticed that it was not necessary to use a whole circle (see armil), and Ptolemy says that he found it more convenient to observe altitudes by means of a square flat piece of stone or wood,
Knight's Mechanical Encyclopedia (ed. Knight), S. (search)
es of an Israelite of Naphtali, a prisoner in Nineveh in the reigns of Shalmanezer and Sennacherib. The statement of Herodotus that the Greeks derived the sundial from the Chaldeans is no doubt correct. In the time of Ahaz, the communications between Assyria and Palestine were open and well traveled, as the Israelites well knew and felt. Homer describes the sun-dial, 950 B. C. The dial was introduced in Athens by Meton, 433 B. C. By L. Papirius Cursor into Rome, 293 B. C. Hipparchus used a dial at Alexandria, 130 B. C. Augustus set one up on a magnificent scale in the Campus Martius. See dial. San′di-ver. (Fr. Suint-de-verre.) A saline scum which rises to the surface of fused glass in the pot, and is skimmed off. Called also glass-gall; sadwei. Sand-jet. A process for grinding and abrading hard substances by the impact of a stream of sand propelled by an air or steam jet. In depolishing glass, the stream of sharp sand is projected by a fan thirty i