Mechanism of the HeavensJ. Murray, 1831 - 621 pages |
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Page xii
... very small inclination to the plane of the ecliptic in which the earth moves ; and on that account , astronomers refer their motions to it at a given epoch as a known and fixed position . The paths xii PRELIMINARY DISSERTATION .
... very small inclination to the plane of the ecliptic in which the earth moves ; and on that account , astronomers refer their motions to it at a given epoch as a known and fixed position . The paths xii PRELIMINARY DISSERTATION .
Page xiii
Mary Somerville. epoch as a known and fixed position . The paths of the pla- nets , when their mutual disturbances are omitted , are ellipses nearly approaching to circles , whose planes , slightly inclined to the ecliptic , cut it in ...
Mary Somerville. epoch as a known and fixed position . The paths of the pla- nets , when their mutual disturbances are omitted , are ellipses nearly approaching to circles , whose planes , slightly inclined to the ecliptic , cut it in ...
Page xv
... epoch for the convenience of astronomical computa- tion , is subject to a minute secular variation of 52 " .109 , occa- sioned by the reciprocal action of the planets ; but as this is also periodical , the terrestrial equator , which is ...
... epoch for the convenience of astronomical computa- tion , is subject to a minute secular variation of 52 " .109 , occa- sioned by the reciprocal action of the planets ; but as this is also periodical , the terrestrial equator , which is ...
Page xxxix
... epoch , the heat of the summers must have been very great , though possibly compensated by the rigour of the win- ters ; at all events , none of these changes affect the length of the day . It appears from the marine shells found on the ...
... epoch , the heat of the summers must have been very great , though possibly compensated by the rigour of the win- ters ; at all events , none of these changes affect the length of the day . It appears from the marine shells found on the ...
Page xlvi
... epoch , and that the vernal equinox of that year should be the first day of the first year . The variations in the positions of the solar ellipse occasion corresponding changes in the length of the seasons . In its pre- sent position ...
... epoch , and that the vernal equinox of that year should be the first day of the first year . The variations in the positions of the solar ellipse occasion corresponding changes in the length of the seasons . In its pre- sent position ...
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Common terms and phrases
A₁ action angle ascending node attraction axes axis B₁ becomes c'mv centre of gravity centrifugal force co-ordinates coefficients comets computed conic sections consequently cosines curve density depending determined differential direction disturbing forces dR dR dt dt earth eccentricity ecliptic elements epoch equal equilibrium equinoxes expression fixed plane fluid functions give hence inclination indefinitely small integral Jupiter's equator Jupiter's orbit latitude mass mean anomaly mean distance mean longitude mean motion moon moon's move nearly nutation observation omitted orbit of Jupiter oscillations parallax perigee perihelion periodic inequalities perturbations planets preceding equation preceding values radius vector ratio regard retrograde motion rotation satellites Saturn secular inequalities secular variations sidereal sine spheroid square substituted surface system of bodies terrestrial theory tion true longitude Uranus velocity whence zero
Popular passages
Page lxviii - the formation of the earth was contemporaneous with that of the rest of the planets ; but they show that creation is the work of Him with whom ' a thousand years are as one day, and one day as a thousand years. 1
Page iv - of elevated meditation. The contemplation of the works of creation elevates the mind to the admiration of whatever is great and noble, accomplishing the object of all study, •which in the elegant language of Sir James Mackintosh is to inspire the love of truth, of wisdom, of beauty, especially of goodness, the highest beauty, and
Page 158 - That the squares of the periodic times of the planets are proportional to the cubes of their mean distances from the sun.
Page lvi - light or heat; its intensity diminishes as the rarity of the air increases ; so that, at a very small height above the surface of the earth, the noise of the tempest ceases, and the thunder is heard no more in those boundless regions where the heavenly bodies accomplish their periods in eternal and sublime silence.
Page l - and open sea, there is a meridian about 30° eastward of the moon, where it is always high water both in the hemisphere where the moon is, and in that which is opposite. On the west side of this circle the tide is flowing, on the east it is ebbing, and on the meridian at
Page lv - in the undulations of an elastic medium. All the principal phenomena of heat may actually be illustrated by a comparison with those of sound. The excitation of heat and sound are not only similar, but often identical, as in friction and percussion ; they are both communicated by contact and
Page xvii - refer Jupiter to a place in which he is not. His true position is in the diagonal of the parallelogram, whose sides are in the ratio of the velocity of light to the velocity of the earth in its orbit, which is as
Page xiii - a discovery,' says Professor Playfair, ' that must render the name for ever memorable in science, and revered by those who delight in the contemplation of whatever is excellent and sublime. After Newton's discovery of the elliptical orbits of the planets, La Grange's discovery of their periodical inequalities is without doubt the noblest truth in physical astronomy
Page xii - begin a new course, thus for ever oscillating about a mean value. This, however, would not be the case if the planets moved in a resisting medium, for then both the eccentricity and the major axes of the orbits would vary with the time, so that the stability of the system would be ultimately destroyed.
Page v - must dwindle into insignificance, or even become invisible ; and that not only man, but the globe he inhabits, nay the whole system of which it forms so small a part, might be annihilated, and its extinction be unperceived in the immensity of creation. A complete acquaintance with Physical Astronomy can only be attained by those who are well versed in the