For the greater part of 1917 from twenty to thirty of these ships sailed back and forth in the Atlantic, always choosing those parts of the seas where they were most likely to meet submarines. They were "merchantmen" of all kinds--tramp steamers, coasting vessels, trawlers, and schooners. Perhaps the most distressing part of existence on one of these ships was its monotony: day would follow day; week would follow week; and sometimes months would pass without encountering a single submarine. Captain Campbell himself spent nine months on his first mystery ship before even sighting an enemy, and many of his successors had a similar experience. The mystery boat was a patient fisherman, constantly expecting a bite and frequently going for long periods without the slightest nibble. This kind of an existence was not only disappointing but also exceedingly nerve racking; all during this waiting period the officers and men had to keep themselves constantly at attention; the vaudeville show which they were maintaining for the benefit of a possible periscope had to go on continuously; a moment's forgetfulness or relaxation might betray their secret, and make their experiment a failure. The fearful tediousness of this kind of life had a more nerve-racking effect upon the officers and men than the most exciting battles, and practically all the mystery ship men who broke down fell victims not to the dangers of their enterprise, but to this dreadful tension of sailing for weeks and months without coming to close quarters with their enemy. About the most welcome sight to a mystery ship, after a period of inactivity, was the wake of a torpedo speeding in its direction. Nothing could possibly disappoint it more than to see this torpedo pass astern or forward without hitting the vessel. In such a contingency the genuine merchant ship would make every possible effort to turn out of the torpedo's way: the helmsman of the mystery ship, however, would take all possible precautions to see that his vessel was hit. This, however, he had to do with the utmost cleverness, else the fact that he was attempting to collide with several hundred pounds of gun-cotton would in itself betray him to the submarine. Not improbably several members of the crew might be killed when the torpedo struck, but that was all part of the game which they were playing. More important than the lives of the men was the fate of the ship; if this could remain afloat long enough to give the gunners a good chance at the submarine, everybody on board would be satisfied. There was, however, little danger that the mystery ship would go down immediately; for all available cargo space had been filled with wood, which gave the vessel sufficient buoyancy sometimes to survive many torpedoes.