Popular AstronomyHarper & Brothers, 1878 - 578 pages |
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Expressions et termes fréquents
angle aperture apparent magnitude appear astronomers atmosphere attraction axis bright cause celestial sphere centre century chromosphere circle comet constellation Copernican system dark described determined diameter direction disk distance diurnal motion earth entirely equator equinox eye-piece focus force glass gravitation heat heavenly bodies heavens hemisphere Herschel Hipparchus horizon inches instrument Jupiter Kepler known latitude latter light longitude magnifying power magnitude Mars mass measures Mercury meridian method miles minutes mirror moon moon's move naked eye nearly nebula node object observations Observatory orbit parallax pass perihelion photosphere planet planetary pole position prism probably proper motion Ptolemy question rays reflecting telescope reflector refracting result revolution revolving right ascension ring rotation round satellites Saturn seen shown sidereal spectroscope spectrum spots stars sun's supposed surface telescope temperature theory tion transit transit of Venus Uranus vapor velocity Venus visible zenith
Fréquemment cités
Page 485 - Their lighter wings. To whom these most adhere, He rules a moment : Chaos umpire sits, And by decision more embroils the fray, By which he reigns : next him, high arbiter, Chance governs all.
Page 306 - Ethereal temper, massy, large, and round, Behind him cast ; the broad circumference Hung on his shoulders like the moon, whose orb Through optic glass the Tuscan artist views At evening from the top of Fesole Or in Valdarno, to descry new lands, Rivers, or mountains, in her spotty globe.
Page 154 - Observer' at a salary of 100£ per annum, his duty being 'forthwith to apply himself with the most exact care and diligence to the rectifying the tables of the motions of the heavens and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting the art of navigation.
Page 485 - Eternal anarchy, amidst the noise Of endless wars, and by confusion stand. For Hot, Cold, Moist, and Dry, four champions fierce, Strive here for mast'ry, and to battle bring Their embryon atoms; they around the flag Of each his faction, in their several clans, Light-armed or heavy, sharp, smooth, swift or slow, Swarm populous...
Page 75 - that every particle of matter in the universe attracts every other particle, with a force whose direction is that of the line joining the two, and whose magnitude is directly as the product of their masses, and inversely as the square of their distances from each other.
Page 440 - I know, has hitherto been noticed by no one, and, indeed, cannot be well observed except with large telescopes. In the sword of Orion are three stars quite close together. In 1656, as I chanced to be viewing the middle one of these with the telescope, instead of a single star, twelve showed themselves (a not uncommon circumstance). Three of these almost touched each other, and, with four others, shone through a nebula, so that the space around them seemed far brighter than the rest of the heavens,...
Page 485 - And time and place are lost ; where eldest Night And Chaos, ancestors of Nature, hold Eternal anarchy, amidst the noise Of endless wars, and by confusion stand : For hot, cold, moist and dry, four champions fierce, Strive here for mastery...
Page 502 - The principle in question may be readily shown in the following way: if a globular, gaseous mass is condensed to one-half its primitive diameter, the central attraction upon any part of its mass will be increased fourfold, while the surface upon which this attraction is exercised will be reduced to one-fourth. Hence the pressure per unit of surface will be increased sixteen times, while the density will be increased only eight times.
Page 509 - At the present time we can only say that the nebular hypothesis is indicated by the general tendencies of the laws of nature, that it has not been proved to be inconsistent with any fact, that it is almost a necessary consequence of the only theory by which we can account for the origin and conservation of the sun's heat, but that it rests on the assumption that this conservation is to be explained by the laws of nature as we now see them in operation. Should any one be skeptical as to the sufficiency...
Page 257 - coming down upon us from the north, would, in thirty seconds after they bad crossed the St. Lawrence, be in the Gulf of Mexico, carrying with them the whole surface of the continent in a mass, not simply of ruin, but of glowing vapor, in which the vapors arising from the dissolution of the materials composing the cities of Boston, New York, and Chicago would be mixed in a single indistinguishable cloud.