The above series of diagrams will show the percentage of safety of ships of different characteristics when coming within the range of visibility of a submarine lying on the ocean highway waiting for passing ships; the submarine is assumed to have a submerged speed of ten knots in each instance. From an analysis of these diagrams it cannot be denied that practically one hundred per cent. safety could be secured could these cargo-carrying submarines cross the ocean from one friendly port to another and remain invisible during the entire journey, but at the present time this is impossible, because there is no known means of supplying sufficient power for long under-water voyages without drawing on the upper air in large quantities to assist combustion in either prime or secondary power-generating machinery. The diagram plainly shows that a cargo-carrying submarine running awash, with her periscope and air intakes only above the water line, may approach within about five and three-quarters miles of any waiting military submarine without danger of being seen, as her "wake" would be below the horizon. Such cargo-carrying submarines can be built and can cross the Atlantic Ocean in this condition at a speed of about ten knots, and by maintaining a sharp lookout would have as much chance of seeing a military submarine as the military submarine would have of seeing them; and by the application of certain tried devices which I do not feel it proper to disclose at this time, but which are within the knowledge of our government authorities, the range of visibility can, I believe, be reduced to less than one mile. This type of vessel can almost instantly become entirely invisible by submerging at the least intimation of danger.