Small hand-held and staff-mount surveying instruments and accessories come in many forms for many purposes. They include such devices as the circumferentor and similar graphometer (described above), surveyor’s sextant, rangefinders, pocket mining transits, hand and reflecting levels, rule clinometers, clinometers/compasses, mountain barometers, measuring chains and tapes, cross-staff heads, spirit levels, artificial horizons, traverse tablets, stadia staffs, surveyor’s slide rules and plumb bobs or plummets. The Abney level, invented in 1870 and called ‘The Miniature Theodolite’, consists of a 4 to 6-inch long rectangular telescope on the side of which is mounted a semicircle arc, graduated in degrees for measuring vertical angles, and a small spirit level. While viewing through the telescope at any angle a mirror reflection of the spirit bubble can be viewed through a small window to line up horizontal or determine an angle of inclination. Rule clinometers are elegantly fashioned multi-purpose instruments. They consist of a thick, hinged, boxwood foot rule in which an inclinometer with vernier scale is mounted at the hinge position. They incorporate a spirit level, retractable alidade sights and brass cased compasses, the latter either stationary or gimbaled. The Crellin's Complete Traverse Table is a simple mechanical traverse marker that operates logarithmically. It consists of a brass tablet with a row of brass levers that can be rotated for counting through 1 to 10, 10 to 100, and 100 to 1000, mush like an abacus. Plumb bobs are quite varied and some large brass or nickel-brass plumb bobs quite elegant. Some come with a detachable end that screws off to give access to a spool with string that feeds out a hole to tie to a tripod, plane table or other devise for leveling.