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Tunnel Transit. 



Under this heading we \vish to say that the general form of the transit-theodolites, 

 described under Nos. 8, 11 and 12, is best adapted for tunnel ngim-cr- 

 ing. The telescope should be inverting and be provided -with a diagonal eye-piece, 

 or a prism. A sensitive striding level should be added to rest on top of the telescope 

 axis to establish the vertical plane correctly. 



The EXTRAS in addition to those enumerated under No. 11, are as follows : 



4*4 ich sensitive striding level, $20.00 



Diagonal eye-piece, 12.00 



Prism, attachable to eye-piece, 8.00 



Lamp, of brass or copper, with ground lens, 7.00 



Small table to attach lamp to standard of transit to illuminate win>>. . 3.00 

 Small reflector in the center of telescope, holes drilled through the telescope 



axis for the illumination of wires, 10.00 



Plummet lamps, $15.00, 10.00, S.OO 



TUNNEL TRANSITS CONSTRUCTED WITH ECCENTRIC TELESCOPE TO ORDER. 



Straight Line Instruments. 



For running Straight Lines on the Surface of the Earth and in Tunnels. 



No. 9 and No. 1C. These Instruments are without circles and graduations. 

 They rest either on three or four leveling screws, and are so arranged as to readily 

 adjust exactly over a given center, after an approximate setting with tripod legs. 

 The telescope axis is of hard bell metal, and reverses in its bearings ; the bearings 

 are adjustable in vertical plane; striding level is provided with a handle in the 

 center and is highly sensitive. We make two sizes, viz. : 



No. 9. Aperture of object-glass, 13/& inches in diameter ; focal length 18 inches ; 

 objects erect or inverted, etc. 



Price $190. 



No 10. Aperture of object-glass, 2 inches ; focal length 18 inches ; etc. 



Price $2 7O. 



With the addition of a glass or spider line micrometer, lamp and reflector for the 

 illumination of the micrometer, both these instruments may be used for taking time. 



"Norm. If deired, an extra striding level can be placed upon two concentric rings of equal diameter* 

 parallel to line of collimation of the telescope, thus making a leveling instrument of great power and precision 

 for long sights. This attachment will cost $35.00. 



