Transactions . Shifting Tripod-Head, Shifting-Plate, Inverted. one from the other (seen also in Fig. 140), forming an equilateraltriangle, to which the thumb and ringers are applied when itis necessary to clamp and unclamp the plate. When the appa-ratus is put together for use, right side up, as in Fig. 140, thethree conical-shouldered leveling-screws of the theodolite are Fig. Shifting Tripod-Head, Clamping-Plate, Inverted. placed in angular cavities in the upper surface of the triangularprojecting ends of Fig. 138, and are then locked in that positionby another thin plate, which has a
Transactions . Shifting Tripod-Head, Shifting-Plate, Inverted. one from the other (seen also in Fig. 140), forming an equilateraltriangle, to which the thumb and ringers are applied when itis necessary to clamp and unclamp the plate. When the appa-ratus is put together for use, right side up, as in Fig. 140, thethree conical-shouldered leveling-screws of the theodolite are Fig. Shifting Tripod-Head, Clamping-Plate, Inverted. placed in angular cavities in the upper surface of the triangularprojecting ends of Fig. 138, and are then locked in that positionby another thin plate, which has a slight horizontal motion,and is thereby secured in a groove by a conical head turned inthe shank of the leveling-screws. Part of this thin plate is REM IRK8 ON MI\ E-Sl R\ EYING INS! Rl MEN I 3. 33 Fig. 140. -i projecting from cinder the (inverted) plate of Fig. Iand it is clamped in position by the milled-headed screw alsoin Fig. 188. The construction and use of thia simple,light and effective apparatus are well known, h is the inven-tion of Troughton & Simms, and is Bupplied with all their in-struments. When the theodolite is locked in position upon this levelingand centering apparatus, and it ie required to center it over afine point marking a Burvey station, it is first done roughly by moving the legs of the tripod-stand, leveling up; and then the clamp-plate, Fig. 13
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
