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accuracy adjustment altitude astronomical axis azimuth barometer base calculated celestial celestial pole centre chronometer circle computed Corr correction curve declination determined dial difference direction earth equal equator error estuary feet fixed stars formula given graduated Greenwich Greenwich mean height high water horizontal hour angle hypsometer iiiii iiiii iiiii inches instant instrument intersection intervals latitude length limb longitude low water lunar mark measured meridian meridian altitude method micrometer miles moon Nautical necessary notch observations obsn obtained parallel perpendicular plane plane-table plotted point of Aries polar pole position prime vertical projection radius readings Refraction right angles right ascension scale screw sextant side sidereal solar sphere spherical trigonometry staff stations straight stream subtended sun's surface survey surveyor tacheometer taken tangent tangential angle telescope temperature theodolite tidal tide transit trigonometry velocity vide fig wire zenith distance
Page 90 - The longitude of a place is the arc of the equator intercepted between the meridian of that place and some assumed meridian to which all others are referred.
Page 137 - ... the column directs the manner in which it is to be applied to mean time to obtain the apparent time. The equation of time, as given on page II, is the apparent time of mean noon; and is equivalent to the hour-angle of the true sun at the instant of mean noon. The sidereal time of mean noon is also the right ascension of the mean sun at Greenwich mean noon.
Page 62 - In any equiangular polygon, any interior angle is equal to twice as many right angles as the figure has sides, less four right angles, divided by the number of angles.
Page 80 - A, 4 cos 6 = cos c cos a + sin c sin a cos B, > (1) . , "cos c = cos a cos b + sin a sin b cos C. J Whence . cos a — cos b...
Page 17 - ... by moving the telescope vertically, and read the two ends. Read the height of the crosswires on the rod. Bring the bubble near the other end of tube and read both the bubble and rod. Repeat many times. Reduce the work by taking the half-difference of the two end readings in each case, thus giving the distance of the centre of the bubble from the centre of tube for each position. Take the mean of these results for each set of end readings separately. If these mean results were for opposite ends...
Page 45 - Where each day's work left off, a fine plumb-line was suspended to mark it off, the plummet vibrating in a brass cup, sunk in the ground and filled with water.
Page 79 - That is, the sines of the sides of a spherical triangle are proportional to the sines of the opposite angles.
Page 128 - Napier has there given a figure, and indicated a method, by means of which they may be proved directly. The rules are curious and interesting, but of very doubtful utility...
Page 10 - ... the plane of the sextant. The simplest test of its perpendicularity is the following. Set the index near the middle of the arc; then, placing the eye very nearly in the plane of the sextant, and near the index glass, observe whether the arc seen directly and its reflected image in the glass appear to form one continuous arc, which will be the case only when the glass is perpendicular.