A surveying transit is a simple, rugged theodolite, often equipped with a compass. It gained popularity during the 19th century with American railroad engineers pushing West. The transit replaced the railroad compass, sextant and Octant_(instrument) and was distinguished by having a telescope shorter than the base arms, allowing the telescope to be vertically rotated past straight down. The transit had the ability to 'flop' over on its vertical circle and easily show the exact 180 degree sight to the user. This facilitated the viewing of long straight lines, such as when surveying the American Wild West. Previously the user rotated the telescope on its horizontal circle to 180 and had to carefully check his angle when turning 180 degree turns. Diagram of an Optical Theodolite. ... Compass in a wooden box A compass (or mariners compass) is a navigational instrument for finding directions on the earth. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... A sextant is a measuring instrument used to measure the angle of elevation of a celestial object above the horizon. ... Octant Octant is a measuring instrument similar to a sextant. ...
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