File:The elements of astronomy; a textbook (1919) (14781896412).jpg

Identifier: elementsofastro00youn (find matches)
Title: The elements of astronomy; a textbook
Year: 1919 (1910s)
Authors: Young, Charles A. (Charles Augustus), 1834-1908 Young, Anne Sewell, b. 1871., ed
Subjects: Astronomy Constellations
Publisher: Boston, New York (etc.) Ginn and Company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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f the Harvard College Observatory for 1896 it is statedthat some experiments recently made there throw a good deal ofdoubt on the objective reality of the doubling. 334. Maps of the Planet.—A number of maps of Mars havebeen constructed by different observers since the first was made byMaedler in 1830. Fig. 84 is reduced from one published in 1888 bySchiaparelli, and shows most of his canals and their gemination.While there may be some doubt as to the accuracy of the minor de-tails, there can be no question that the main features of the planetssurface are substantially correct. The nomenclature, however, is in avery unsettled condition. Schiaparelli has taken his names mostlyfrom ancient geography, while the English areographers,1 followingthe analogy of the lunar maps, have mainly used the names of astrono-mers who have contributed to our knowledge of the planets surface. 1 The Greek name of Mars is Ares, hence Areography is the descrip-tion of the surface of Mars. 236 MARS. (§ 334
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§ 336) SATELLITES. 237 335. Temperature.—As to the temperature of Mars wehave no certain knowledge at present. Unless the planethas some unexplained sources of heat it ought to be very cold.Its distance from the sun reduces the intensity of solar radi-ation upon its surface to less than half its value upon theearth, and its atmosphere cannot well be as dense as at thetops of our loftiest mountains. On the other hand things lookvery much as if liquid water and vegetable life were presentthere. It is earnestly to be hoped that before long we maycome into possession of some heat-measuring apparatus suffi-ciently delicate to decide whether the planets surface is really intensely cold or reasonably warm, — for of coursethere are various conceivable hypotheses which might accountfor a high temperature at the surface of Mars. 336. Satellites. — The planet has two satellites, discoveredby Hall, at Washington, in 1877. They are extremely small,and observable only with very large telescop

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