A Treatise on Astronomy

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Harper & brothers, 1866 - 338 من الصفحات
 

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الصفحة 128 - RULES TO KNOW WHEN THE MOVEABLE FEASTS AND HOLYDAYS BEGIN. EASTER DAY, on which the rest depend, is always the First Sunday after the Full Moon which happens upon, or next after the Twenty-first Day of March ; and if the Full Moon happens upon a Sunday, Easter Day is the Sunday after.
الصفحة 266 - 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.
الصفحة 287 - The names of the signs of the zodiac are: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces.
الصفحة 309 - ... too remote to be separated into their component stars. Lord Rosse himself was careful to point out that it would be unsafe from his observations to conclude that all nebulosity is but the glare of stars too remote to be resolved by our instruments. In 1858...
الصفحة 139 - ... at last brought down to the ground; and the greater the velocity is with which it is projected, the farther it goes before it falls to the earth. We may therefore suppose the velocity to be so increased, that it would describe an arc of 1, 2, 5, 10, 100, 1000 miles before it arrived at the earth, till at last, exceeding the limits of the earth, it should pass into space without touching it.
الصفحة 68 - A solar day is the interval between two successive returns of the sun to the same meridian. The sun moves through 360 degrees of longitude in one tropical year, or 365 days, 5 hours, 48 minutes, and 47 sec« onds. Hence the sun's mean daily motion in longitude is found by the proportion One year : one" day : : 360° : 59
الصفحة 55 - ... most curious effects of atmospheric refraction is the oval form of the disks of the sun and moon, when near the horizon. This arises from the unequal refraction of the upper and lower limbs. The latter being nearer the horizon is more affected by refraction, and therefore raised in a greater degree than the upper limb, the effect of which is to bring the two limbs apparently closer together, by the difference between the two refractions. The form of the disk is therefore affected as if it were...
الصفحة 185 - The mean interval between the moon's passage over the meridian, and high water at any port on the days of new and full moon, is called the establishment of the port. The mean interval at New York is 8h. 13m., and the difference between the greatest and the least interval occurring in different parts of the month is 43 minutes.
الصفحة 48 - G, which carries the whole of the upper works, and also a pointer, to show the degree and nearest five minutes to be read off on the azimuth circle ; the remaining minutes and seconds being obtained by means of the two reading microscopes, C and D. The pillars HH support the transit axis, I, by means of the projecting pieces, LL. The telescope, MM, is connected with the horizontal axis in a manner similar to that of the transit instrument.
الصفحة 50 - ... is used, the upper limb will appear as the lower, and vice versa ;* the angle shown on the instrument, when corrected for the index error, will be double the altitude of the sun's limb above the horizontal plane ; to the half of which, if the semi-diameter, refraction, and parallax be applied, the result will be the true altitude of the centre.

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