Outlines of Astronomy |
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Page 2
... once . We can now understand a little better what is meant when we are told that the Earth's diameter is eight thousand miles ; for if a pin's head on a ball a yard thick is large enough to represent a great mountain on the Earth , we ...
... once . We can now understand a little better what is meant when we are told that the Earth's diameter is eight thousand miles ; for if a pin's head on a ball a yard thick is large enough to represent a great mountain on the Earth , we ...
Page 19
... once . But it has been applied to all remarkable appearances in the sky , such as comets and northern lights , as well as shooting stars . However , modern writers in English gen- erally apply the name only to those comparatively small ...
... once . But it has been applied to all remarkable appearances in the sky , such as comets and northern lights , as well as shooting stars . However , modern writers in English gen- erally apply the name only to those comparatively small ...
Page 28
... once in the time during which every part of its rim has once touched the track . In counting the rotations of any thing , then , we need something to reckon from , which we can consider fixed and motionless . But we know that the ...
... once in the time during which every part of its rim has once touched the track . In counting the rotations of any thing , then , we need something to reckon from , which we can consider fixed and motionless . But we know that the ...
Page 37
... in the figure is coarser than that which is usually seen . A few faculæ appear near some of the spots close to the limb ; and the two zones of spots are shown . 63. The average number of spots visible at once varies. Plate 1 .
... in the figure is coarser than that which is usually seen . A few faculæ appear near some of the spots close to the limb ; and the two zones of spots are shown . 63. The average number of spots visible at once varies. Plate 1 .
Page 37
... once in every eleven years ; but two maxima are not always just eleven years apart . For example , there was one maximum in 1848 ; the next did not come till 1860 ; and the next came in 1870. A minimum of spots usually comes not half ...
... once in every eleven years ; but two maxima are not always just eleven years apart . For example , there was one maximum in 1848 ; the next did not come till 1860 ; and the next came in 1870. A minimum of spots usually comes not half ...
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Common terms and phrases
aphelion appear astronomers atmosphere axis ball body bright calculations called celestial objects celestial sphere circle clock clouds comet compared consider course cross determined direction disk distance Earth Earth's atmosphere Earth's centre Earth's orbit Earth's rotation ecliptic equal equator equatorial stars exactly eye-piece fact farther Hence Hipparchus horizon Jupiter kind known latitude law of gravitation laws of motion length lens less light limb longitude look Mars mass mean measure ment meridian meteors miles Moon Moon's movement nearer nearly nodes north pole northern noticed nutation object-glass observations opposite orbit parallax particular passing pencil perihelion perpendicular photosphere plane prism refraction regard retrograde revolution right ascension ring round the Sun satellites Saturn seen shape side sidereal sidereal day solstice sometimes spectrum spots stars straight line Sun's suppose surface telescope terrestrial place tion transit triangle Uranus usually Venus vernal equinox vertical visual angle zenith
Popular passages
Page 82 - The squares of the periodic times of any two planets are to each other, in the same proportion as the cubes of their mean distances from the sun.
Page 201 - the eclipse presented, during the total obscuration, a vision magnificent beyond description. As a centre stood the full and intensely black disc of the moon, surrounded by an aureola of soft bright light, through which shot out, as if from the circumference of the moon, straight massive silvery rays, seeming distinct and separate from each other, to a distance of two or three diameters of the lunar disc ; the whole spectacle showing as upon a background of diffused rose-coloured light...
Page 320 - It will be seen that we multiply the denominator of the dividend by the numerator of the divisor for the denominator of the quotient, and the numerator of the dividend by the denominator of the divisor for the numerator of the quotient.
Page 224 - Surfaces of spheres are to each other as the squares of their diameters.
Page 298 - ... directly proportional to the product of the masses and inversely proportional to the square of the distance between them.
Page 390 - The limits of the obliquity of the apparent ecliptic to the equator ^are 24° 35' 58" and 21° 58' 36"; whence it follows that the greatest and least declinations of the sun at the solstices can never differ from each other to any greater extent than 2° 37
Page ii - BROTHERS, In the Office of the Librarian of Congress at Washington. CAMBRIDGE: PRESS OF JOHN WILSON AND SON.
Page 375 - Astronomical Observations and Researches made at Dunsink, the Observatory of Trinity College, Dublin,
Page 193 - The greatest number of eclipses that can happen in a year is seven; five of the sun and two of the moon, or four of the sun and three of the moon.
Page 296 - Every body continues in its state of rest or of uniform rectilinear motion unless compelled to change its state by forces impressed upon it.