Bausch & Lomb 1908 catalog of Engineering Instruments

7 inch Complete Transit Theodolite

This instrument has been used on important work as, for example, by the Canadian and United States governments in boundary surveys. It is well adapted for time and latitude observation, as well as triangulation and general survey work. We have supplied them to nearly all the leading colleges of this country. as it is particularly well adapted for purposes of instruction.

The U-shaped standards are employed in construction, great strength resulting from their being cast in one piece. The graduations of the horizontal circle are on a beveled edge, and read to 30" by two opposite verniers, the circle being divided into 1/3 degree. Attached reading glasses are provided for both the horizontal and the vertical circles if desired. The vertical circle is 5 1/2" in diameter and reads to 30" by double opposite verniers. Both the circle and the verniers are fully protected by covering guards. The telescope is inverting. The extra long center is of steel, resting in a cast-iron bearing, giving strength, durability and smoothness of motion, thus permitting extra sensitive levels.

Other Specifications

The horizontal circle has a diameter of 7" inside of the graduations, and 8 1/8" outside. The graduations are in 1/3 degrees, and read to 30" by double opposite verniers. The vertical circle has a diameter of 4 1/2" inside the graduations, and 5 1/2" outside. This circle also reads to 30" by double opposite vemiers.

The erecting telescope is 13" in length, with a power of 22 and 35 diameters. The effective aperture is 1 1/2" and the apparent field 36 degrees.

The telescope level is 4 3/4" long, and each division is sensitive to 10" of arc. The graduations are 2 mm. apart. The standard levels are also graduated in 2 mm. divisions, each division having a value of 30" of arc, The striding level to the telescope axis is graduated like the others, and each division represents 10" of arc.

The range of shifting center is 1/2". Three (not four) German silver leveling screws are provided.

The instrument is 14 1/2" in height, and weighs approximately 20 lbs., in carrying case 35 lbs., and 70 lbs. packed for shipment. The split-leg tripod weighs approximately 8 3/4 lbs., and when packed for shipment 21 lbs. The extension tripod weighs about 10 lbs., or 22 1/4 lbs. when packed for shipment.