MATHEMATICAL INSTRUMENTS. PART IV. SURVEYING INSTRUMENTS. SURVEYING Consists in the measurement of such distances and angles, as shall most correctly, and conveniently, define the boundaries of a plot of ground, as well as the positions of the various objects that diversify its surface, whether natural, as hills, rivers, forests, &c, or artificial, as roads, railways, canals, &c. From the measurement thus made, these boundaries and objects can be laid down on paper, so as to preserve their relative magnitudes and positions, the observed measurements being all reduced in the same proportion. The features of the ground thus laid down, form what is called a map or plan, according as the plot of ground represented is of greater or smaller extent; and the process of laying it down is called plotting the survey. The instruments used in plotting, and also in the copying, reduction, and measurement, of maps and plans, are fully described in the volumes on Mathematical J)rawing, Measur ing, and Optical Instruments. It remains, then, to describe: (1) The instruments used for measuring horizontal distances; (2) the instruments used for measuring vertical distances; and (3) the instruments used for measuring angles. B THEIR CONSTRUCTION, ADJUSTMENT, Enlarged Edition, for the most part entirely re-written VOL. III. SURVEYING AND ASTRONOMICAL INCLUDING I.-INSTRUMENTS USED FOR DETERMINING THE GEOMETRICAL II.-INSTRUMENTS EMPLOYED IN ASTRONOMICAL OBSERVATIONS JF. HEATHER, M.A. LATE OF THE ROYAL MILITARY ACADEMY, WOOLWICH; AUTHOR OF "PRACTICAL 60 DESCRIPTIVE GEOMETRY," ETC., ETC. Capio Yumen LONDON CROSBY LOCKWOOD AND SON 7, STATIONERS' HALL COURT, LUDGATE HILL 1891 |
