What is "traverse board"

Traverse \Trav"erse\, n. [F. traverse. See Traverse, a.]

1. Anything that traverses, or crosses. Specifically:

   1. Something that thwarts, crosses, or obstructs; a cross accident; as, he would have succeeded, had it not been for unlucky traverses not under his control.

   2. A barrier, sliding door, movable screen, curtain, or the like.

      Men drinken and the travers draw anon.
      --Chaucer.

      And the entrance of the king, The first traverse was drawn.
      --F. Beaumont.

   3. (Arch.) A gallery or loft of communication from side to side of a church or other large building.
      --Gwilt.

   4. (Fort.) A work thrown up to intercept an enfilade, or reverse fire, along exposed passage, or line of work.

   5. (Law) A formal denial of some matter of fact alleged by the opposite party in any stage of the pleadings. The technical words introducing a traverse are absque hoc, without this; that is, without this which follows.

   6. (Naut.) The zigzag course or courses made by a ship in passing from one place to another; a compound course.

   7. (Geom.) A line lying across a figure or other lines; a transversal.

   8. (Surv.) A line surveyed across a plot of ground.

   9. (Gun.) The turning of a gun so as to make it point in any desired direction.

2. A turning; a trick; a subterfuge. [Obs.] To work a traverse or To solve a traverse (Naut.), to reduce a series of courses or distances to an equivalent single one; to calculate the resultant of a traverse. Traverse board (Naut.), a small board hung in the steerage, having the points of the compass marked on it, and for each point as many holes as there are half hours in a watch. It is used for recording the courses made by the ship in each half hour, by putting a peg in the corresponding hole. Traverse jury (Law), a jury that tries cases; a petit jury. Traverse sailing (Naut.), a sailing by compound courses; the method or process of finding the resulting course and distance from a series of different shorter courses and distances actually passed over by a ship. Traverse table.

   1. (Naut. & Surv.) A table by means of which the difference of latitude and departure corresponding to any given course and distance may be found by inspection. It contains the lengths of the two sides of a right-angled triangle, usually for every quarter of a degree of angle, and for lengths of the hypothenuse, from 1 to 100.

   2. (Railroad) A platform with one or more tracks, and arranged to move laterally on wheels, for shifting cars, etc., from one line of track to another.

The traverse board is a memory aid formerly used in dead reckoning navigation to easily record the speeds and directions sailed during a watch. Even crew members who could not read nor write could use the traverse board.

As the mathematician William Bourne remarked in 1571, “I have known within these 20 years that them that were ancient masters of shippes hathe derided and mocked them that have occupied their cards and plattes and also the observation of the Altitude of the Pole saying; that they care not for their sheepskinne for he could keepe a better account upon a board.”

Bourne’s ‘old salt’ is talking about a traverse board, a wooden board with a compass rose drawn on it linked by pegs and cords to a series of peg holes beneath it. It allowed a helmsman to keep a rough check of the time sailed on each rhumb of the wind.