Elements of Astronomy, for Schools and Academies with Explanatory Notes, and Questions for Examination

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Sheldon and Company, 1872

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Page 270 - They are also alike in external appearance, presenting to view a black, shining crust, as if the body had been coated with pitch. This crust is not greater than the two-hundredth part of an inch in thickness, its composition is identical with that of the mass, it bears the marks of fusion, and strikes fire with the flint. When broken, the surface of the fracture displays the color of an ashgrey. " Distinct aerolites," says Berzelius, the celebrated chemist, " are frequently so like one another in...
Page 49 - Circles are great circles passing through the zenith of an observer, and perpendicular to his horizon. The vertical circle passing through the east and west points of the horizon is called the Prime Vertical ¡ that passing through the north and south points coincides with the celestial meridian.
Page 278 - For, if the sun and moon are on the same side of the earth, they both pull the same way, and their attractive power is united ; if they are on opposite sides...
Page 265 - Rcnier and an assistant, at Planchettes, a village about sixty miles to the northeast of that city. In the space of seven and a half hours, the number of meteors observed by the six observers at Geneva was 381 ; and during five and a half hours, the number observed at Planchettes by two observers was 104.
Page 48 - ... the sun. More Accurate Computations. — A more accurate determination of the phases as visible at any point of the earth's surface may be obtained from the Besselian elements which are given for every ten minutes of Greenwich mean time. Their geometric signification is as follows: — Let us imagine a plane passing through the centre of the earth, perpendicular to the right line joining the centres of the sun and moon. This latter line is the axis of the moon's shadow, and the plane is called...
Page 195 - The third and last, that the squares of the periodic times of the planets are as the cubes of their mean distances from the sun.
Page 103 - ... intersection of the plane of its orbit with the plane of the earth's equator, a retrograde motion upon the former plane ; and since that plane is inclined at a very small angle to the plane of the ecliptic, this would produce a like retrograde motion of the equinoctial points upon the ecliptic.
Page 247 - ... relation to its elongation, the same degree of brightness always corresponding to the same position of the satellite in relation to its primary. Now this is an effect which would be explicable on the supposition that different sides of the satellite reflect light with different degrees of intensity, and that it revolves on its axis in the same time that it revolves round its primary. It has been observed that, when the satellite has eastern elongation, it has ceased to be visible, from which...
Page 118 - December 37 for the sake of convenience. This inclination is ever varying, as well from the effect of its mean diminution, as of the nutation of the earth's axis: it is an important element in deducing...
Page 193 - The weight of an object above the surface of the earth varies inversely as the square of its distance from the center of the earth.

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