## A Treatise on Surveying, Volumen2 |

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accuracy altitude astronomical axis azimuth barometer boat calculated celestial celestial pole centre chronometer circle clinometer computation convergence Corr correction curve declination determined dial difference earth equal equator error fixed stars formula gauge given Greenwich Greenwich mean height high water horizontal hour angle hypsometer inches instant instrument intersection intervals latitude length longitude low water lunar mark mean sea level measured meridian method miles minutes moon nautical nautical miles necessary notch 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 semi-diurnal sextant side sidereal soundings sphere spherical triangle spherical trigonometry staff Star's stations straight stream subtended sun's surface survey lines surveyor taken tangent tangential angle telescope theodolite tide tide-gauge transit trigonometry velocity vide fig wire zenith distance

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Página 136 - ... 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.

Página 147 - Ocean, the first thing which strikes us is, that, the north-east and south-east monsoons, which are found the one on the north and the other on...

Página 79 - Having given two sides and the included angle, or two angles and the included side.

Página 69 - ... often takes many hours) before it can be considered fit for use ; and, if this precaution be not attended to, the whole E of the work, after having set very hard on the surface, cracks and becomes a friable mass, from the slaking of the refractory particles after the body of the concrete has set. The reader is referred, for further information on this subject, to the volume of this series on " Foundations and Concrete Works.

Página 44 - 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. In 1791, when the work of the Ordnance Survey was resumed, it was decided to re-measure this base with a steel chain. Two chains of 100 feet in length were prepared by Pamsden. Each chain consisted of 40 links, half an inch square in section, with brass handles flat on the under side, a transverse line on each handle marking the length of...

Página 88 - A, and therefore the latitude of a place is equal to ' the altitude of the cdatial pole as observed at that place.

Página 78 - That is, the sines of the sides of a spherical triangle are proportional to the sines of the opposite angles.

Página 59 - It is equal to half the angle which the chord subtends at the centre of the circle of which the curve is an arc, or if PC be a whole chord of 100 feet, half the degree of curve. The 'deflection angle

Página 45 - The lines defining the yard are in the axis of the bar. The length of the bar is that at 62° F., and is fixed by Act of Parliament which declares that " the pendulum vibrating seconds of time in a vacuum in the latitude of London, at the level of the sea, is 39-1393 inches of the standard, and that the yard shall be in the proportion of 36 to 39-1393 inches.

Página 75 - It jis usual, and convenient, to assume that the three intersecting planes are bounded by a ' spherical surface' of unit radius, having its centre at the common point 'of intersection. The three planes therefore, cut the bounding sphere in great circles. (A great circle is the intersection of the surface of a sphere with a plane passing through the centre. Its radius is therefore, equal to that of the sphere, ride Part I.).