Cathetometer

1. n. An instrument for the accurate measurement of small differences of height; esp. of the differences in the height of the upper surfaces of two columns of mercury or other fluid, or of the same column at different times. It consists of a telescopic leveling apparatus (d), which slides up or down a perpendicular metallic standard very finely graduated (bb). The telescope is raised or depressed in order to sight the objects or surfaces, and the differences in vertical height are thus shown on the graduated standard.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.