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Bausch & Lomb 1908 catalog of Engineering Instruments

4 inch Standard Theodolite

In this instrument we offer a compact theodolite of small weight but great efficiency. It is particularly well adapted to such surveys as those carried on by the various departments of the U. S. government, and considerable numbers have been furnished for this purpose. This theodolite is also used for the Magnetic Survey as inaugurated by the Department of Terrestrial Magnetism of the Carnegie Institution.

The U-standard, now universally adapted for instruments without magnetic needle, is used in construction. These standards being cast in one piece, give extraordinary lateral strength and rigidity obtainable in no other way.

The horizontal circle of this instrument has a beveled edge. The graduations on a circle of this size are consequently very easily read, and the possibility of parallax is also greatly lessened. Opposite verniers with attached reading glasses permit readings to 30". The vertical circle also has opposite verniers with attached reading glasses and is covered. A level is mounted on the vernier frame of the vertical circle for its control.

No compass is regularly furnished with the theodolite. but on order we can supply a box compass with 4" needle, which can be readily mounted between the standards. Two posts are attached to this compass, permitting it to be placed upon the plate and engaging in two holes in the plate, thus assuring a fixed position in relation to the telescope. This instrument is made with three leveling screws only.

Other Specifications

The horizontal circle has a diameter of 4 1/2" inside the graduations. and 5 1/2" outside the graduations, which read to 30" by double opposite verniers. The vertical circle has a diameter of 3 1/4 inside the graduations, and reads to single minutes by double opposite verniers.

The inverting telescope has a length of 7 1/2", power of 20 diameters, effective aperture of 1 1/4", and an apparent field of 36 degrees.

The telescope level is 2 7/8" long, and is graduated in 2 mm. divisions, each division being sensitive to 20 seconds of arc. The plate levels are also graduated in 2 mm. divisions, each division being sensitive to 6o seconds of arc. The standard level is similarly graduated, and has the same sensitiveness.

The striding level to the telescope axis is 3 1/4" long, is graduated in 2 mm. divisions, and each division is sensitive to 20" of arc.

This theodolite is 11 1/2 in height, and weighs approximately 10 1/4 lbs. In carrying case the approximate weight is 20 lbs., and when ready to ship, 35 lbs. The ordinary tripod weighs approximately 8 3/4 lbs., and when packed for shipment, 23 lbs. The extension tripod weighs 10 lbs. and 24 1/4 lbs. respectively.

90 4" Standard Theodolite, as specified and illustrated, including split-leg tripod, . . 300.00
Compass Box, for 4" standard theodolite . . . . . . . . . . . 15.00

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