Naval History and Heritage Command

Memorandum, Rear Admiral Ralph Earle, Chief of the Bureau of Ordnance

NAVY DEPARTMENT

BUREAU OF ORDNANCE

Washington, D.C.

CONFIDENTIAL

CIRCULAR LETTER NO. 402.

To: (See list attached.)

Subject: Destruction of enemy mines.

Inclosure: (A) One blueprint of mine safety tools. (Herewith)1

     1.   The following information is submitted with view to use in case of planting of enemy mines along our coasts.

     2.   On discovery of any mines, report should be made at once.

     When reporting the mine, the following points should in every case be obtained: (1) shape (2) number of horns (3) whether central horns or not (4) color (5) appearance (as regards time in water) (6) number painted on mine (if conditions permit observation of same).

     If any vessels strikes a mine, the position of the ship when mined is the true position of the mine. It may be presumed that the line of mines runs across rather than along the channel route, and care must be observed to avoid any other mines possibly in the vicinity.

     The appearance of a floating mine and also the number has proved the means on several occasions of recognizing the mine field from which it comes.

     Particular care should be take that the position of any mine observed is accurately noted.

     3.   Floating mine should be sunk by gun fire. If possible the firing ship should be at least 200 yards distant from the mine, but if this is impracticable, approach may be made to not less than 120 yards. All the crew are to be instructed to take cover during the operation. If a mine sinks without exploding, do not steam over the position until sufficient time has elapsed for it to have reached the bottom, as it may explode on hitting the bottom.

     4.   In case a mine is washed up onto the beach, it will very probably be out of commission. It should be towed out to deep water, using a line of not less than 300’ length, and sunk, or destroyed on the beach by exploding a small wrecking charge lashed to it. The latter procedure should not be adopted if there are any persons or buildings in the vicinity which might be injured by the explosion.

     5.   In case it is desired to salvage the mine, the following procedure should be followed: (a) withdraw, when possible, safety gear as described below, (b) remove horns: this can be done with absolute safety after (a) has been done, (c) up end the mine and remove detonator with primer.

     Great care must be taken to avoid damage to the horns before the safety gear is withdrawn.

     The tools shown in the sketch will be supplied to the Naval Districts as soon as available; requisitions therefor need not be submitted.

     To put the safety gear in the safe position the following procedure is to be followed:- the tools consist of a strong back (1), a screwed spindle (2), which is guided in the strong back to prevent it from turning, and a wing nut (5). In addition a wedge piece (6) is provided for insertion in the slot of the safety gear.

     The spindle (2) is screwed into the safety gear spindle. The strong back (1) is placed over it, the feet entering the screwed ring, and the wing nut is screwed up so withdrawing the safety gear spindle until the wedge piece (6) can be inserted in the slot in the safety gear spindle. The pin (9) is then inserted in the wedge piece to prevent its dropping out.

     Removal of horns.- The horns should then be removed by means of the spanner (15), Fig. 2, which is provided.

     To remove detonator.- The tool shown in Fig. 2 consisting of strong back (9), screwed for (10), hand nut (12), pin (13), and lanyard (14), are used for this purpose.

     The strong back (1) is carefully placed in position in the screwed ring as shown in Fig. 2.

     The fork (10) is unscrewed until the pin (13) can pass through it and the eye of the detonator.

     The hand nut (12) is screwed up hard, withdrawing the detonator until it can be removed by hand.

<Ralph Earle>