The Elements of Astronomy, Physical and Geometrical, Volume 2 |
Common terms and phrases
Aftronomers alfo almoft alſo Angle Apfes Apfis Apogeum appear Atmoſphere Axis becauſe befides Body cafe Center Centripetal Force Circle Circle of Latitude Comet conftruction defcrib'd defcribe defin'd determin'd Difc diminiſh'd Diſtance drawn Duplicate Ratio Earth Eclipfe Ellipfis encreas'd enlighten'd equal Equation Excentricity faid fame manner fecond feen fhew fhewn fide fince firft firſt Fix'd Stars fome fometimes forefaid foregoing Prop ftance fuch fuppofe fuppos'd given goes thro Gravity greateſt horizontal Parallax Interfection itſelf Jupiter laft Latitude Latus rectum leaft lefs Libration Longitude Lunar mean Anomaly Mercury moft Moon Moon's Motion mov'd muſt Nodes obferv'd Obfervation oppofite Orbit Parabola Parallax Penumbra Perihelium perpendicular Phænomena plac'd Place plain Plane pofition Point Primary Planet produc'd PROPOSITION Quadratures reafon refpect requir'd Right line Ring Satellite Saturn SCHOLIUM Semidiameter Shadow ſpace Sun's Syftem Syzygies thefe theſe thofe thoſe Trajectory Triangle urg'd Venus Volva whence whofe wou'd
Popular passages
Page 885 - Hyperbolic Motion, or a Motion swifter than what a Comet might acquire by its Gravity to the Sun, 'tis highly probable they rather move in very Excentric Elliptic Orbits, and make their returns after long periods of Time: For so their number will be determinate, and, perhaps, not so very great. Besides, the space between the Sun and the Fix'd Stars is so immense, that there is room enough for a Comet to revolve, tho' the Period of its revolution be vastly long.
Page 887 - Hence, I think, I may venture to foretel, that it will return again in the Year 1758. And, if it should then so return, we shall have no Reason to doubt but the rest may return also : Therefore Astronomers have a large Field wherein to exercise themselves for many Ages, before they will be able to know the Number of these many and great Bodies revolving about the common Center of the Sun, and to reduce their Motions to certain Rules.
Page 462 - The Discovery of a New World ; or, a Discourse tending to prove that it is probable there may be another habitable World in the Moon ; with a Discourse concerning the possibility of a passage thither.
Page 886 - Motions, and that which indeed induced me to construct it, is, that whenever a new Comet shall appear, we may be able to know, by comparing together the Elements, whether it be any of those which...
Page 891 - Sun to the Northwards of the Way of the Earth. At which Time, had the Earth been there, the Comet would have had a Parallax equal to that of the Moon, as I take it. This is fpoken to...
Page 890 - Parallax will become very fenfible; and the Proportion thereof to that of the Sun will be given. Wherefore fuch Tranfits of Comets do afford us the very...
Page 886 - I my felf have feen return, and obferv'd in the Year 1682. All the Elements agree, and nothing feems to contradict this my opinion, befides the Inequality of the Periodic revolutions. Which Inequality is not fo great neither, as that it may not be owing to Phyfical Caufes. For the Motion of Saturn is fo difturbed by the reft of the Planets, efpecially Jupiter, that the Periodic time of that Planet is uncertain for fome whole days together. How much more therefore will a Comet be fubjeft to fuch like...
Page 668 - The Orb of the attracting Power which is in the MOON, is extended as far as the Earth, and draws the Waters under the torrid Zone...
Page 887 - And since looking over the histories of comets I find, at an equal interval of time, a comet to have been seen about Easter in the year 1305, which is another double period of 151 years before the former. Hence I think I may venture to foretell that it will return again in the year 1758.
Page 886 - ... appeared before, and consequently to determine its period, and the axis of its orbit, and to foretell its return.