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according added adjusting angle answering apparent apparent altitude apparent distance applied arch azimuth called co-secant co-sine computed contained correction corresponding declination determined Diff difference direct dist divided Earth eclipse equal equation error EXAMPLE feet fixed star give given glass greater greatest Greenwich half height hence horizon horizontal parallax interval known latitude length less limb logarithm longitude lower mean meridian method minutes Moon Moon's motion move natural Nautical nearly necessary nonagesimal noon object observed obtained orbit parallel passing period place of observation planet pole position PROBLEM proper quadrant quantity reduced refraction remainder Required right ascension rising RULE secant semidiameter ship sine star subtracted Sun's Table taken tangent telescope third transit True altitude true distance variation watch zenith
Page 38 - ... space is much more rapid than what has now been stated ; or while she accompanies the earth in its motion round the sun, which is at the rate of 68,000 miles an hour, she also moves thirteen times round the earth during the same period, which is equal to a course of nearly twenty millions of miles. The moon's orbit is inclined to the ecliptic in an angle of 5° 9...
Page 6 - AY and night arise from the circ uoarotatiou of the Earth. That imaginary line about which the rotation is performed, is called the Axis, and its extremeties are called Poles. That towards the most remote parts of 'Europe is called the North Pole, and its opposite the South Pole. The Earth's Axis being produced will point out the Celestial Poles. The Equator is a great circle on the Earth* every point of which is equally distant from the Poles ; it divides the Earth into two equal parts, called...
Page 19 - This way of considering the sun is of the utmost importance in its consequences. That stars are suns can hardly admit of a doubt. Their immense distance would perfectly exclude them from our view, if the light they send us were not of the solar kind.
Page 272 - That Mr Harrison's watch cannot be depended upon to keep the longitude within a degree in a West India voyage of six weeks ; nor to keep the longitude within half a degree for more than a fortnight ; and then it must be kept in a place where the thermometer is always some degrees above freezing...
Page 43 - ... produced very sensible effects, and the motion of the Comet would have suffered the greatest disturbance. In such case the plane and species of its Ellipsis and its periodic Time would have been very much changed, especially from meeting with Jupiter. In the late descent, the true path of this Comet left the Orbits of Saturn and Jupiter below itself a little towards the South : It approached much nearer to the paths of Venus and Mercury, and much nearer still to that of Mars. But as it was passing...
Page 45 - Newton, we must not omit to state, that the germ of it, and something more, had been previously published by Hooke. In giving an account of the inventions of members of the Royal Society, Sprot mentions " a new instrument for taking angles by reflexion, by which means the eye at the same time sees the two objects both as touching on the same point, though distant almost to a semicircle, which is of great use in promoting exact observations at...
Page 19 - It appears to me now, that we cannot refuse to admit such a motion, and that indeed it may be as evidently proved as the diurnal motion of the earth. Dark spots, or large portions of the surface less luminous than the rest, turned alternately in certain directions either towards or from us, will account for all the phenomena of periodical changes in the lustre of the stars so satisfactorily, that we certainly need not look out for any other cause.
Page 21 - A star of the eighth magnitude, with a faint luminous atmosphere of a circular form, and of about 3' in diameter. The star is perfectly in the centre, and the atmosphere is so diluted, faint and equal throughout, that there can be no surmise of its consisting of stars, nor can there be a doubt of the evident connexion between the atmosphere and the star.
Page 94 - Commons came to the following resolution : " /.. -.,/.,.'. That it is the opinion of this...
Page 20 - On our sun these spots are changeable. So they are on the star o Ceti; as evidently appears from the irregularity of its changeable lustre, which is often broken in upon by accidental changes, while the general period continues unaltered. The same little deviations have been observed in other periodical stars , and ought to be ascribed to the same cause.