SUBMARINE-CHASERS

A real menace came when the U-boat commander popped his periscope out of the sea and saw several little motor-boats bearing down upon him. They seemed harmless enough, but a moment's inspection showed them to be armed with guns fully as powerful as those he carried. It was useless to discharge a torpedo at so speedy and small a foe. A torpedo has to have a fairly deep covering of water, else its course will be disturbed by surface waves; and the submarine-chasers drew so little water that a torpedo would pass harmlessly under them. It was useless for the U-boat commander to come up and fight them with his guns. They would have been upon him before he could do that, and their speed and diminutive size made them very difficult targets to hit. Besides, he dared not risk a duel of shell, for he knew that if the precious inner hull of his boat were punctured, he could not seek refuge under water; and if he could not hide, he was lost. The little armed mosquito craft swarmed about the harbor entrances, ready to dash at any submarine that showed itself. They could travel twice as fast as the submarine when it was submerged and half again as fast as when it was running on the surface.

Submarines had to take to cover when these chasers were about. Herr Kommandant did not even dare to take a look around through his periscope, because the streak of foam that trailed in its wake would betray him and immediately the speedy motor-boats would take up the chase; and they had a disagreeable way of dropping bombs which, even if they did not sink the submarine, might produce such a concussion as to spring its seams. His foes had discovered one of his most serious defects. He was blind under-water and they were making the most of this handicap.

Forward End of a U-boat. Note the Four Torpedo Tubes Behind the Officer

Groping along under-water by dead-reckoning was not any too safe a procedure near land, because he was liable at any moment to crash into an uncharted rock or maybe into the wreck of some submarine victim. He could not correct his bearings without coming to the surface, and, in the black depths of the sea, a slight miscalculation might send him to his doom. As was explained in the previous chapter, he had to keep moving, because he could not remain suspended under water.

A Depth-bomb Mortar and a Set of "Ash Cans" at the Stern of an American Destroyer

He was more helpless than a ship sailing in the densest of fogs. A ship can stop and listen to sound-signals, or even to the beating of the surf on the shore, or it can take soundings to locate its position; and yet it is no uncommon occurrence for a ship to run ashore in a fog. How much easier it is for a submarine to lose its bearings when obliged to travel by dead-reckoning, particularly in the disconcerting excitement of the chase! To avoid the danger of collision with surface vessels, the commander chose to run at a depth of sixty-five feet. That was the upper limit of his safety-zone. A depth of over two hundred feet was his lower limit, because, as stated before, the water-pressure at that depth would crush in his hull or at least start its seams. If the bottom were smooth and sandy, and not too deep, he could settle gently upon it and wait for darkness, to make his escape.

But while he lay on a sandy bottom, he was still in danger. Trawlers were sweeping the bottom with nets. He might be discovered; and then if he did not come up and surrender, a bomb would let in the sea upon him.