180 



Transit-Theodolite. 



For us.- in <-iti->, in 1 uniii>ls. an. I fur t riaiiy ulat ion. 



No. 11. Many years ago we found it desirable t<. .l.-si-u a transit for uso 

 when instruments of ordinary construction would fail to giv<> satisfaction, or 

 do not permit of rapid work where the highest degree of accuracy is ivqum-ii. 

 The instrument as shown in the accompanying illustration has no compass, and, 

 therefore, the upper frame mounting the telescope is in one piece, which is pro- 

 vided with ribs, and which rests directly on the top-flange of the inner center. 

 The result of this is that great lateral strength is obtained, which permits of 

 mounting the telescope axis by means of cylinders at each end in \\yes. On top 

 of each bearing of the telescope axis is mounted a cap provided with an adjusting 

 screw, with which the necessary friction for the revolving telescope is obtained, 

 and these caps are also provided with two milled-headed screws, \\hirh can be re- 

 moved readily when the telescope is to be reversed for straight line measurements 

 over the bearings. These caps are so arranged as to completely exclude dust 

 from the axis. In this new arrangement the telescope can be reversed as in ordi- 

 nary instruments through the standards, as well as over the bearings, as is usual 

 in triangulation and for aligning straight lines; and last, but not least, the move- 

 ment of the telescope in the vertical plane is the most accurate known. Ordinary 

 transits cannot fulfil these functions owing to the peculiar form of the hearings 

 wherein the telescope axis revolves, which bearings are so made to give lateral 

 stiffness to the telescope, on account of the slenderness of the standards resting 

 on the upper plate. Many of these instruments are in use in the survey and tri- 

 angulation of our largest cities and have given great satisfaction. The Instrument 

 is provided with three or four leveling screws. The verniers can be placed at right 

 angles to the line of sight, or as shown in the cut. The dimensions, etc., are : 



Horizontal plate, 6^ inches, graduation on solid silver protected as in our regular 

 engineers' instrument; two double opposite verniers, reading to 30"; two rows of 

 figures in opposite directions; long compound centers; 11-inch telescope; (invert- 

 ing or erect); 1^ inches clear aperture; power 24 diameters ; protection to object- 

 slide; single spring tangent screws for the upper and lower plates; 4 leveling 

 screws; shifting center, split-leg tripod, case, etc. 



"Weight of instrument with a 7-inch circle, and all complete, 14 Ibs. ; weight of 

 tripod l l / 2 Ibs. 



Price, for Plain Transit-Theodolite, $24O.OO. 



Extras to Plain Transit-Theodolite. 



For Extras to Tunnel Transits, see Extras to Mining Transits. 



Horizontal limb 6% inches in diameter, verniers reading to 20"* . . 810.00 



" " 7 " " " 10"* . . . 35.00 



Vertical arc 5 " " minutes, . . 20.00 



Full 5 inch vertical circle, " " 25.00 



" double opposite " " 50.00 



Two reading glasses, with ground glass shades to verniers, . . . 15.00 



Instrument provided with 3 leveling screws, as in cut, 10.00 



^Shifting center for instrument with 3 leveling screws (improved) . . 5.00 



Stadia wires, fixed, 3.00 



Striding level,** 20.00 



6 inch spirit-level with reversible clamp, tangent and gradienter to telescope, 40.00 

 Oblong compass, with motion for setting off the variation. (Three-inch 



needle reads only a few degrees each way from zero.) .... 20.00 



These graduations should always be ordered with reading glasses and ground glass shades attachtd to the 

 instrument. 



Unless ordered to the contrary the striding level of this instrument will not rest directly over the point* 

 of contact in wyes as represented in Transit No. 12. For greater convenience it rests on the telescope axis at 

 points between the standards, which has the advantage that the striding level can be left on the axis while the 

 telescope is revolved in the vertical plane. A striding level should always be ordered with an instrument of the 

 class described above. 



NOTE. A Plain Transit-Theodolite is without a level, clamp and arc to telescope. 



For increase of aperture in inverting telescopes see note to Transit No. 1, page 142. 

 t NOTE. For description, use, etc., of our shifting center for a transit with three leveling screws, see manual. 



