The "depth charge" is a submarine bomb, so constructed that it is discharged at any determined depth of water when thrown overboard. If the water is 100 feet deep the bomb will explode at that depth. The bombs are used to drop in places where the submarine has been located or is expected of lurking in the bottom of the sea. While the exploding bomb may not strike the underseas boat it will create havoc on board the underwater craft if discharged in close proximity, the extra water pressure exerted causing disarrangement of the delicate mechanism, if not rendering the boat unfit for service.
Some of the patrol boats of the English have been armed with "lance bombs." These are bombs of highly explosive character which are fastened to the end of a long pole or staff. They are used just as a harpoon is used when by chance a submarine may emerge from the water in too close proximity to the chaser. It is not of record that any U-boats have been sunk with these strange javelins, but official reports show that the boats are armed with them for emergencies.
CHASER TROUBLES THE SUBMARINE.
What with dragging bombs through the water, and setting traps and nests for the submarines, the chasers make great trouble for the underseas craft, but the ingenious Germans are constantly on the alert, and it has been proved that in one or two instances at least the submarines cut their way through the heavy chain nets which were set to catch them near Havre. It was said that the submarine was provided with steel knives or wire cutters, and shears operated by electricity or pneumatic pressure, which enabled the boat to cut its way through the barrier of chains and wires.
As a means of visualizing the operations of the "chaser" and giving some idea of the excitement which attends the attempt to run down the underseas craft, the following description by an English sailor is interesting. The chase occurred off the Isle of Wight:
"Offshore a short distance was a patrol boat lying very low and flying distress signals. We had run over to her and learned that about an hour before the periscope of a submarine had been stuck up not far from her, then the craft had submerged, appeared again about a mile away, and fired four shots, which let in enough water slowly to sink the patrol, which before the war had been nothing but a dirty little trawler.
"Finding the crew of the patrol could take care of themselves in their small boats and learning that the submarine had run over to the westward, where we knew chain net traps to be laid, we circled in that direction.
"Our powerful motors thrummed evenly. The water seemed to part ahead of us, and the gunners squinted along the surface, looking for the glimpse of a periscope or the first sign of the hull of the U-boat if she should be proceeding awash.
CREW THRILLED WITH JOY.
"Suddenly, off to the west, we made out her periscope. Intense joy thrilled our little crew. She was inshore from us. She was between our circular course and the chain nets—in the trap. The periscope we had seen might be a dummy, for a submarine frequently casts loose a phoney periscope to draw fire, but, at any rate, she must have been between us and the nets if she cut it loose.