36. Depth Charge Marker Mk 1 Mod 1 is for day use to indicate the point of depth charge barrages and to provide a reference point for further search and attack in daylight ope-rations against submarines. It spreads a bright green slick over an area approximately 50 by 20 feet, which is visible for approximately an hour from the deck at distances up to 2.5 miles under normal conditions. The marker is 11.9 inches long and 3.5 inches in dia-meter, weighing approximately 3.5 lbs. It consists of two cylindrical kraft paper contain-ers, each of which holds 1.375 lbs. of fluorescein dye, joined together by a wood block which houses the fuze assembly. This assembly is of the Bouchon igniter type and ignites a 30-gram charge of black powder in a spirally wound celluloid tube, which extends in to the kraft paper dye containers. The firing mechanism is held in a safe condition by a ring pull pin, which holds a safety lever against the wood block. This lever holds the firing pin against the action of a spring and away from the primer. The cross section of the marker will be seen in Fig. 10.

Figure 10. – Depth Charge Marker Mk 1 Mod 1 (For Day Use)

Operation

37. Depth Charge Marker Mk 1 Mod 1 should be launched by hand at a point approxima-tely time until the marker leaves the hand. Once released, the lever falls free and the spring snaps the firing pin against the primer in the fuze assembly. The primer flash igni-tes a length of time fuze which delays the flash into the 30-gram black powder charge in the celluloid tube approximately 15 seconds from the time the safety lever is released. The ignition of the 30-gram black powder charge bursts the kraft paper containers and scatters the dye.

Packing

38. Each Depth Charge Marker Mk 1 Mod 1 is encased in an asphalt-impregnated paper mailing tube sealed by a strip of adhesive tape. Ten markers are shipped in a wood case. General instructions for use are printed on the mailing tubes.

Stowage

39. General pyrotechnics stowage and handling rules as outlined in paragraphs 9 to 12, inclusive, apply to Depth Charge Marker Mk 1 Mod 1. If exposed to excess moisture, the fluorescein dye in the marker my cake, so that its dispersal in the water may be conside-rably reduced.

Safety Precautions

40. In preparing and launching Depth Charge Marker Mk 1 Mod 1, the following should be rigidly enforced:

(a) The safety pin must not be removed until the marker is held in the hand ready for launching.

(b) The safety lever must be held firmly against the side of the wood block while the safety pin is pulled and until the marker is cast overboard.

(c) If the marker is accidentally dropped on deck after the safety pin has been pulled, the area must be cleared of all personnel at once and must remain cleared until after the marker fires. No attempt should be made to retrieve the fallen marker, as it cannot again be made safey once the safety lever ahs sprung free.