The American practical navigator, being an epitome of navigation and nautical astronomy (1903)
Bowditch, Nathaniel, 1773-1838, United States. Navy Dept. Bureau of Equipment, Logan, George Wood, 1868-1915 · Washington, Govt. Print. Off. · leaf 136
rc of exactly 180°, for the purpose of adjusting the line of collimation. On top of the rule near itscenter is the level—sometimes replaced by two levels at right angles—by means of which it may be seenwhen the table is in a true horizontal position. A magnetic needle mounted in a rectangular metal… … 417. To be in correct adju.«tment, a plane table must comply with the following conditions: («) The fiducial edge of the rule must be perfectly straight, {b) The level must have the bubble inits central position when the table is truly horizontal, (c) The vertical cross hair must be perpendic-ular…
Navigation · Nautical astronomy
Internet Archive · California Digital Library · Public Domain Mark 1.0. Free to use for anything.
