These will be subdivided as follows:

In each company assigned to the mine defense, a permanent manning table will be made out and always kept up to date. A copy of this manning table will be posted in the mine commander’s station. In addition, a copy of such portion of this table as pertains to any particular station will be posted therein.

Plotting board.—The plotting board differs from that used for guns in that it requires no gun arm and corresponding attachments. Furthermore, since the distance at which mines are planted will in general be small, the board, without any change in size, may be used with a much larger scale, say, 150 yards or even 100 yards to the inch, and the arms graduated accordingly.

The stations are manned during the planting of mines and the location of distribution boxes, as well as during operations.

FIG. 15.—PREDICTION RULER.

For planting buoys signals may be made from the primary, from the secondary, or from both, as conditions warrant.

Observations are taken on each mine as planted, the data are recorded, and the position of each mine is plotted.