A Treatise on Mathematical Instruments: Including Most of the Instruments Employed in Drawing, for Assisting the Vision, in Surveying and Levelling, in Practical Astronomy, and for Measuring the Angles of Crystals: in which Their Construction, and the Methods of Testing, Adjusting, and Using Them, are Concisely Explained |
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accuracy adjustment altitude arc of excess artificial horizon attached axis azimuth beam compasses bisected bubble called chain chords chromatic dispersion clamping screw coincide compass box constructed correct cross wires described diameter diaphragm difference direct image Ditto ditto divided drawing edge equal eye-piece feet field of view figure focal length goniometer Gunter's chain half hinge-joint horizon glass horizontal angles horizontal limb inches index error index glass instru instrument intersection latitude lens lenses line of collimation line of sines logarithmic marked means measured ment meridian moved object object-glass observed parallax parallel plate screws passing perpendicular plane position primary divisions prism protractor radius rays reading reflected image reflector refraction represent right ascension round scale sextant side sixth column socket spirit level square staff station strument tangent screw telescope theodolite transit transverse distance Troughton's truly horizontal tube turning vernier plate vernier scale vertical circle zero