Such a type of vessel travelling with a freeboard of five feet would become visible to a submarine lying in ambush when she approached within eight miles. This increases the area of danger from one hundred and three square miles, as shown in diagram, position No. 1, in the first instance to two hundred and one square miles, as per diagram corresponding to position No. 2, but in comparison with the usual type of surface cargo-carrying ship of the so-called tramp type she is comparatively safe, as she has the ability to submerge in less than two minutes; and it is hardly likely that she would be attacked without warning, for fear she might be a friendly military submarine. Any communication in the way of wireless, sound, or other signals would, if she were a merchant ship, give her warning, and she would at once submerge, as her only business would be to deliver her cargo and not communicate with or expose herself to _either friend or foe_. When far from land she might take a chance and navigate entirely on the surface with a freeboard of fifteen feet, in which condition she can make a speed of eleven knots, as her position No. 3, on the surface of the ocean. This increases the danger area to about three hundred and thirty square miles, as on diagram, position No. 3, about three times the danger area shown on position No. 1, but as the area to be covered by the military submarine on the high seas, far from land, is also much greater, the real danger would be proportionately less than that with the lower visibility in a more thickly infested zone. [Illustration: TORPEDO BEING FIRED FROM THE DECK TUBES OF THE SUBMARINE "SEAL" This vessel was fitted with two double-barrel torpedo guns, housed in a superimposed superstructure. These four torpedoes could be fired to either broadside. The above photograph shows a torpedo in the act of leaving one of these tubes above water. They may be discharged either above or below the surface.]