=Smoke Screens.=--To hide vessels in clouds of smoke so as to avoid being seen by submarines has been proposed as a method for eluding the U-boats. This procedure would really assist submarine commanders in their search for prey, for the smoke would notify them of the presence of vessels far below the horizon, whose location and course they would otherwise not be aware of. They have a term in the British navy called "firing into the Brown," which means firing at a group of vessels, expecting that a certain percentage of hits will be made, depending on how close a formation of ships is being kept; firing into the "smoke" would be apt to get some. Smoke screens can be used effectively only when the wind happens to be proportionate to the speed of the ships and blowing in the right direction. With a head wind or a strong side wind some of the vessels forming the convoy are sure to be exposed to attack. =Zigzag.=--Steering zigzag courses adds to the time of crossing from one port to another, and affords only a slight measure of additional safety, as a ship running a zigzag course takes much longer to make a crossing, and is therefore longer exposed to danger; besides, this process adds very materially to the cost of the voyage. It probably does add somewhat to her chances of escape, as a submarine lying in wait anticipating that she will pass within torpedo range might be fooled by her zigzagging out of the way. On the other hand, a submarine might be lying in wait too far to one side of her course to be able to intercept her, and the ship might just as likely as not, not knowing she was there, zigzag right toward her and get caught. In facing the submarine problem, the nations at war with Germany are thus forced to adopt tactics of three kinds: First, to destroy the enemy submarines--I have been informed from reliable sources that England has over five thousand vessels searching for U-boats; second, to make cargo vessels invulnerable to torpedo attacks; and, thirdly, to elude and escape the U-boats. No great measure of success, no great results, have come out of attempts of the first two orders; the U-boats have in general gone unscathed, and they have inflicted damage of such an appalling nature as to terrify those cognizant of the shipping needs of Europe. In my judgment, however, efforts to combat the submarine should be concentrated on devising ways and means to elude it; this is the only solution which promises results. I shall therefore devote the remainder of this chapter to a discussion of the problem of eluding submarines and how it may best be accomplished. =Cargo Submarines.=--In my judgment, the only way that any nation will be able ultimately to continue its commerce with any degree of safety or certainty when blockaded by submarines will be by the construction of large merchant submarines which will be able to evade the enemy U-boats successfully.