CHAPTER VIII.THE MINE COMMAND.
A mine command consists of the mine groups and rapid-fire batteries specifically assigned for their protection, which are controlled by a single individual.
The mine commander is in direct command of the elements of the mine defense during drill and action. His station is at the mine primary, which is connected by telephone to the battle commander’s station. He bears the same relation to the battle commander as do the fire commanders, and his duties are similar to theirs.
The mine commander is responsible that the property officer requests for all matériel necessary to carry out the approved scheme for mining the harbor; he is responsible, further, that the property officer keeps this matériel in proper condition for immediate service.
The senior company officer of the mine command is the property officer and obtains from the district artillery engineer all necessary matériel for the mine defense. He has direct charge of the storeroom, cable tanks, loading room, wharves, boats, boathouses, and mining casemate. The personnel of the mine companies are subject to his orders for service in connection with caring for and maintaining this matériel.
The officers of the companies of the mine command will be assigned by the mine commander in accordance with their special fitness.
The enlisted personnel of mine companies will be divided into sections, detachments, and details, as follows:
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.
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.
During operations vessels may be tracked by the vertical or by the horizontal method of position finding. If by the former, either the command “Fire” may be given when the vessel is on the cross wires of the instrument set at the range and azimuth of a mine, or the time from any point to the instant of passing over a mine may be found by means of the prediction ruler (see below) and the command “Fire” be given at the proper instant, as indicated by the stop watch. For the horizontal base system the latter method must be used.
Prediction ruler(fig. 15).—This is a 10-inch white celluloid slide rule with a beveled edge. The slide is graduated in “Yards in 15 seconds,” and on the left and right of the runway, respectively, are a “Fire at time” and a “Yards to mine” scales. The beveled edge is graduated from the center outward in both directions with “0” in the center of the scale and “500” at either end. Each 50 and 100 has its value engraved on the scale.
Method of using.—Plot the position of the target for a 15-second interval. With the beveled edge find the distance the target has passed over during the interval; and also determine the distance from the last plotted position to the mine. Move the slide until the graduation corresponding to the “Yards in 15 seconds” is opposite the graduation corresponding to the “Yards to mine,” and read the “Fire at time” scale opposite the arrow on the slide. The reading will be the number of seconds from the last plotted position to the mine which the vessel is approaching. A stop watch is started at the time of the last observation on the target, and at the expiration of the time obtained from the “Fire at time” scale the command “Fire” may be given.
Observation firing.—The mine commander’s station is connected with the casemate by telephone. At the command “Observation firing”sent to the casemate, the casemate operator will seethat all automatic switches are up, and that all firing switches are open. He will then close the double circuit breaker, and switches 4 and 9, which will energize the busses of the power panel. At the command “Group ——, mine ——,” the operator will close switches 3 and 8 on the power panel, thereby putting both D. C. and A. C. power on the operating boards. At the command “Ready,” given from the mine commander’s station at the proper time, the operator will stand ready to trip the corresponding automatic switch. At the command “Fire” the automatic switch will be tripped and the firing switch will be closed. Without delay, after the mine is fired, the firing switch and the power switch will be opened, the automatic switch closed up, and the mine switch opened on the mine block.
If the mine is struck before the command “Fire” is given, the automatic switch will fall, and the mine should be fired by closing the firing switch unless there are positive orders to the contrary.
Contact firing.—For contact firing the mine system will be set so that a signal will be sent to the casemate and the mine will be fired when the latter is struck by a passing vessel. This is the normal method of firing in actual service. At the command “Contact firing,” which may be given for all groups, or certain individual ones, the casemate operator will seethat all automatic switches are up, power and mine switches closed, and firing switches open; he will then close the double circuit breaker, and switches 4, 9, 3, and 8 on the power panel. This puts both D. C. and A. C. on the operating boards. He will then close the firing switches on all the boards or on such as may have been indicated. When a mine has been fired, the corresponding mine block will be cut out.
If it is desired to delay the firing of a mine after being struck, the command “Delayed contact firing” is given. The operations are the same as for contact firing except that the firing switch is closed by the operator a short time after the mine has been struck or when directed to do so. After the mine has been fired the firing switch will be opened, and the corresponding mine block will be cut out.