The Elements of Astronomy: Or, The World as it Is, and as it Appears

Crocker and Brewster, 1850 - 376 pages
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Page 344 - ... that the mean longitude of the first satellite, minus three times that of the second, plus twice that of the third, is always equal to two right angles.
Page 37 - Now, suppose the head of the screw to be a circle, whose diameter is an inch, the circumference of the head will be something more than three inches : this may be easily divided into a hundred equal parts distinctly visible. If a fixed index be presented to this graduated circumference, the hundredth part of a revolution of the screw may be observed, by noting the passage of one division of the head under the index. Since one entire revolution of the head moves the point through the fiftieth of an...
Page 213 - 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 22 - The Latitude of a star is its angular distance from the ecliptic measured on a circle of latitude.
Page 13 - A sphere is a solid terminated by a curved surface all the points of which are equally distant from a point within called the centre.
Page 272 - The radial force, or that part of the disturbing force which acts in the direction of the line joining the centres of the sun and disturbed planet, has no effect on the areas, but is the cause of periodical changes of small extent in the distance of the planet from the sun. It has already been shown, that the force producing perfectly elliptical motion varies inversely as the square of the distance, and...
Page 13 - The radius of a sphere, is a straight line drawn from the center to any point of the surface.
Page 38 - Now, the arc of a circle, subtended by one second, is less than the 200,000th part of the radius, so that on a circle of 6 feet in diameter it would occupy no greater linear extent than part of an inch ; a quantity requiring a powerful microscope to be discerned at all.
Page 268 - But such a personification of "force" is a remnant of barbaric thought, in no wise sanctioned by physical science. When astronomy speaks of two planets as attracting each other with a " force " which varies directly as their masses and inversely as the squares of their distances...
Page 131 - It is, therefore, partly to this cause, and partly to those we have developed above, that the slight deviations we now perceive must be attributed. " Such is a summary of the hypothesis of La Place on the origin of the solar system. This hypothesis explains, in the most satisfactory manner, the three most remarkable phenomena presented by the planetary motions. " 1st. The motion of the planets in the same direction, and nearly in the same plane.