A Treatise on Astronomy, Descriptive, Physical and Practical: Designed for Schools, Colleges, and Private Students |
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Page 9
... sun's declina- nation is more than 23 ° north ( as it is on and about the 20th of June in each year ) , then the sun comes at , or very near , the northern horizon , at midnight ; it is nearly east , at 6 o'clock in the morning ; it is ...
... sun's declina- nation is more than 23 ° north ( as it is on and about the 20th of June in each year ) , then the sun comes at , or very near , the northern horizon , at midnight ; it is nearly east , at 6 o'clock in the morning ; it is ...
Page 10
... sun's diurnal circle is above the the center of the sun's di . horizon , and the observer will have more than 12 hours sun- urnal tion . tled . mo- light . When the sun is on the equator , the horizon , of every lati- tude , cuts the ...
... sun's diurnal circle is above the the center of the sun's di . horizon , and the observer will have more than 12 hours sun- urnal tion . tled . mo- light . When the sun is on the equator , the horizon , of every lati- tude , cuts the ...
Page 18
... sun ( 25. ) When we examine the sun's passage across the meridian , and compare the elapsed intervals with the sidereal clock , we find regular and progressive variations , above and below a mean period , that cannot be accounted for by ...
... sun ( 25. ) When we examine the sun's passage across the meridian , and compare the elapsed intervals with the sidereal clock , we find regular and progressive variations , above and below a mean period , that cannot be accounted for by ...
Page 21
... sun's center at the instant the sun crosses the celestial equa- tor in the spring , on the 20th of March . Right ascension is measured from the first meridian , east- ward , on the equator , all the way round the circle , from 0 to 360 ...
... sun's center at the instant the sun crosses the celestial equa- tor in the spring , on the 20th of March . Right ascension is measured from the first meridian , east- ward , on the equator , all the way round the circle , from 0 to 360 ...
Page 31
... sun's center the instant the sun comes to the celestial equator , in the spring ( which point on the equator is called the equinoctial point ) ; but the difficulty is to find exactly where ( near what stars ) this meridian line is ...
... sun's center the instant the sun comes to the celestial equator , in the spring ( which point on the equator is called the equinoctial point ) ; but the difficulty is to find exactly where ( near what stars ) this meridian line is ...
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Common terms and phrases
altitude apogee apparent diameter argument argument of latitude ascending node astronomers attraction axis called celestial celestial equator central eclipse CHAP circle clock comet compute conceive conjunction corresponding declination degrees determine difference Digits eclipsed earth earth's orbit eccentricity equa equal equator equinox Evection fixed stars full moon give gravity greater greatest Greenwich heavens Hence horizon horizontal parallax inferior planet interval Jupiter Kepler's Kepler's third law less lunar orbit magnitude mass Mean Anomaly mean distance measure Mercury meridian altitude miles minutes MOON'S HOURLY MOTION moon's motion moon's path nearly node nutation observations opposite perigee period planet pole position proportion radial force radius refraction represent result revolution right angles right ascension round satellites Saturn semidiameter sidereal sine solar sun and moon suppose tance tangent telescope tion transit triangle true tude Uranus variation velocity Venus zenith
Popular passages
Page 144 - Jupiter a moderate-sized orange, in a circle nearly half a mile across; Saturn a small orange, on a circle of four-fifths of a mile; Uranus a full-sized cherry, or small plum, upon the circumference of a circle more than a mile and a half, and Neptune a good-sized plum on a circle about two miles and a half in diameter.
Page 139 - ... appearances of spots seen upon them, render it extremely probable that they subsist in the atmosphere of the planet, forming tracts of comparatively clear sky, determined by currents analogous to our trade-winds, but of a much more steady and decided character, as might indeed be expected from the immense velocity of its rotation. That it is the comparatively darker body of the planet which appears in the belts is evident from this, — that they do not come up in all their strength to the edge...
Page 143 - Venus a pea, on a circle 284 feet in diameter; the Earth also a pea, on a circle of 430 feet; Mars a rather large pin's head, on a circle of 654 feet; Juno, Ceres, Vesta, and Pallas, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange, in a circle nearly half a mile across...
Page 80 - For, by the first of Kepler's laws, the areas described by the radius vector are proportional to the times, and when this is the case, by Art.
Page 118 - The squares of the times of revolution are to each other as the cubes of the mean distances from the sun.
Page 144 - As to getting correct notions on this subject by drawing circles on paper, or, still worse, from those very childish toys called orreries, it is out of the question.
Page 141 - ... and less strongly marked than those of Jupiter, and owing doubtless to a similar cause. That the ring is a solid opake substance, is shown by its throwing its shadow on the body of the planet on the side nearest the sun, and on the other side receiving that of the body.
Page 154 - ... is leaving behind, must seem gradually to approach, in the same manner as when we walk through a forest, the ranges of trees to which we advance are constantly widening in their apparent distance from each other, while the distance of those we leave behind is gradually contracting.
Page 147 - Gregorius, of Constantinople, in June, 1337, whose course he describes very accurately. Comets do not all move from west to east, like the planets. Some have a direct, and some a retrograde motion. Their orbits are not comprehended within a narrow zone of the heavens, like those of the principal planets ; they vary through all degrees of inclination. There are some whose plane is nearly coincident with that of the ecliptic, and others have their planes perpendicular to it. Indeed, a slight inclination...
Page 89 - Whenever the sun is above the horizon of any place, that place is receiving heat; when below, parting with it, by the process called radiation ; and the whole quantities received and parted with in the year...