Transactions . d or rough hand-pressure is appliedto turn the telescope over vertically. In the general design ofthe new transit-theodolite under discussion, it was, therefore,decided that it should have comparatively low standards orYs, and a long and powerful telescope, to suit the divisions ofthe circles and be capable of sighting to the bottom of thedeepest shafts—conditions incompatible with the old Englishform of construction. To carry this idea into effect, the horizontal axis-socket intowhich the telescope is, in ordinary cases, generally screwed intwo parts, one on each side, was made
Transactions . d or rough hand-pressure is appliedto turn the telescope over vertically. In the general design ofthe new transit-theodolite under discussion, it was, therefore,decided that it should have comparatively low standards orYs, and a long and powerful telescope, to suit the divisions ofthe circles and be capable of sighting to the bottom of thedeepest shafts—conditions incompatible with the old Englishform of construction. To carry this idea into effect, the horizontal axis-socket intowhich the telescope is, in ordinary cases, generally screwed intwo parts, one on each side, was made larger and much longerthan usual, and the middle part of the telescope-tube was alsomade in one piece, turned as nearly true as possible with respectto its optical axis, fitted into the aforementioned horizontalaxis-socket or sleeve, and caused to slide a defined distance init by turning the special milled head of a rack-and-pinion xxxi.—54 sss AN LMlMtoVKI) FORM OK TKA NSIT-TII KOIHJMTK. Fig I,. Dennerts and Papes Theodolite. \N l IIPROA BD FORM OF rRANSIT I 111 .1 i WTien, therefore, a sight ie required, as in Pigs. 2 and ;<. to betaken through the telescope and the center of the Instrumentdown a vertical Bhaft, the telescope is Blid through the axis-socket, or hub, until the object-glass end in revolving will clearthe cross spirit-level tube fixed upon the vernier-circle. Thefocusing for clear vision of an object is then made in the usualway. On the other hand, when the object to be observed hasgreat elevation, or, as the case may sometimes require, be in thezenith, the telescope is slid through the axis-socket, or sleeve,in the opposite direction, or until the eye-end of the telescope,carrying the micrometer-box and circle and the long diagonal -piece, will, as in Fig. 4, pass the vernier-circle. A clearview \ terrestrial or celestial objects can then be obtained onturning the ordinary focusing-screw. When the instrument is employed in land-surveying,
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
