=Nets; Plates.=--There have been many devices proposed for warding off the torpedoes, the usual weapon of the submarine. The most common of these schemes designate the use of nets or plates suspended from booms carried out from the sides of the ship and extending down into the water. Any device of this kind seriously handicaps the ship's speed, and, if she is once sighted by a submarine, is almost sure to be come up with and attacked. Plates, to be effective against a broadside attack, would need to be the full length and extend to the full depth of the ship. Now, skin friction of a ship's plating is the principal resistance to be overcome in forcing a ship through the water up to speeds of about ten knots, the average speed of the cargo-carrying ship. If you increase the speed beyond ten knots, other resistances come more prominently into effect, such as wave-making resistance, etc. Now a ship afloat has two sides, while a plate suspended in the water equal to the length and depth of the ship also must have two sides, and thus presents nearly the same square feet of plate surface to the friction of the passing waters as the two sides of the ship, and two plates, one on each side, present nearly twice the area and thus very materially reduce the speed. This resistance is further augmented by the roll and pitch of the vessel, and in a severe storm the plates would be unmanageable and of great danger to the ship itself. The resistance of nets with its vertical members is much greater than that of plates. To get some idea of what the resistance of a vertical rod extending down into the water is, take a broom handle and attempt to hold it vertical when it is extended down into the water from a launch running at about ten knots; it is almost impossible to hold it. A net with a mesh fine enough to catch a torpedo would consist of thousands of vertical members as well as horizontal members extending down into the water. I have been informed by one naval architect of standing who investigated this phase of the problem that nets of sufficient strength to protect the sides of a ten-knot ship from a torpedo attack cut the speed of the ship from ten knots down to two and one-half knots per hour. It would therefore take a ship protected in this way four times as long to make her voyage; her chance of discovery would therefore be four times as great and her chance of destruction, if once discovered, be almost certain, as a submarine could readily overtake her and plant mines in her course or even tow a mine underneath her bottom and explode it there, which would destroy the ship much more completely and quickly than a Whitehead torpedo exploded against her side. Devices have also been developed which enable a torpedo to dive under a net and explode under a ship's bottom by a slightly delayed detonator.