In considering the practicability or value of these devices, we must first consider the capabilities of the submarine and the proper tactics for her commander to pursue. In a paper read before the Institution of Naval Architects in London, in 1905, I described, illustrated by diagrams, the proper method to be pursued in attacking a surface ship, in which I contended that the commander of a submarine, on sighting an enemy, should always keep the hull of his own boat below the horizon in its relation to the enemy vessel, and try to intercept the approaching vessel by taking frequent observations of her course and speed. When the two vessels approach sufficiently near to make it possible for the larger surface vessel to observe the smaller submarine (the comparative range of visibility being proportionate to the exposed surfaces of the two vessels above the horizon), the submarine should then entirely submerge, with her telescopic periscope withdrawn below the surface of the water to avoid the making of a "wake"—which looks like a white streak on the water. When the commander wishes to make an observation he should first bring his submarine to rest and then extend the periscope above the surface for a brief instant only, and thus avoid the chance of being seen. Earlier in the war it was common to detect the submarine by her wake, but now, since the fitting of merchantmen with guns, the above tactics are usually pursued, and the first intimation the crew has of the presence of the submarine is the shock of the explosion caused by the torpedo "striking home."

GERMANY'S U-9 AND SOME OF HER SISTER SUBMARINES

AEROPLANE AND SUBMARINE
(Drawing by T. E. Lake.)

For defense of coast lines aeroplanes and submarines may work in conjunction. Aeroplanes, with their enormous range and high speed can locate surface ships many miles away, beyond the range of a submarine's periscope or sound-detecting devices. It could then direct the submarine by wireless or direct communication. Aeroplanes, however, are of great danger to enemy submarines. Flying at certain altitudes they can see submarines a short distance below the water and swoop down on them, dropping depth bombs or trailing torpedoes.

Aeroplanes and Dirigibles.—These are undoubtedly valuable near land in shallow water, providing the water is clear and has a bottom in striking contrast to the hull of the submarine. I should consider the dirigible likely to prove of more value than the aeroplane, owing to its ability to hover directly over and regulate its speed to that of the submarine and thus enable itself to drop depth bombs more accurately. Experience has shown that it is almost impossible to calculate where a bomb will strike when dropped from a swiftly moving aeroplane. The chance of its striking the submarine would be very slight. The use of aeroplanes has, however, forced the submarines away from shoal clear water and probably has been instrumental, also, in causing them to become equipped with high-angle rapid-firing guns. In a battle between swiftly moving aeroplanes and submarines with high-powered guns firing shrapnel, the chances are nearly all in favor of the submarine, as they can carry the most powerful guns and are firing from a much more stable platform; in fact, the best analogy I can think of is that of a gunner in a "blind" firing at a flock of ducks passing overhead. Aeroplanes have been used, however, as scouts, merely to detect a submarine and direct surface ships to the attack; also, aeroplanes have directed trawlers to a submarine lying submerged at a shallow depth. This method of attack has undoubtedly been successful in some instances, but where success might have been met with in this manner with the earlier submarine boats, which were not provided with guns, it is now a problem easily met by submarine architects. Submarine boats may be built which have no fear of this combination. One of my earliest designs provided for a revolving armored turret to carry heavy-calibre guns; this revolvable armored turret would extend only above the surface and would carry guns of sufficient calibre to sink any trawler, destroyer, or other craft except an armored ship. It has recently been reported that the Germans are bringing out ships fitted with turrets of this type, and as they are familiar with my designs from the Patent Office specifications, and also have my working drawings of a large cruiser submarine mounted with guns, in 1905, I have no doubt that the report is true, as they have consistently been the first to adopt such new devices as may be needed to offset any attack against their submarines, or to increase their means of offence against surface craft without relying upon torpedoes alone. As far back as 1902 the Protector was fitted with a small gun on top of her conning tower, with the breech extended into the sighting hood and a tampon controlled from within the turret for closing the muzzle, so that no water would enter the barrel when the vessel was submerged, thus permitting a new cartridge and shell to be inserted into the breech when submerged; then, by momentarily bringing the conning tower above the surface, we could fire, then submerge and reload, rest and fire again, etc., thus providing a disappearing gun on a very stable platform.

In deep water the submarine may readily escape detection by aeroplanes by sinking below the depth to which vision can penetrate. This depends upon the amount of foreign substance held in suspension in the water. Along the Atlantic coast it is possible to see only a few feet; as you go off shore vision becomes clearer, and it would probably vary during the dry seasons from four to five feet near shore to forty or fifty feet well off shore. The greatest distance I was ever able to see in my experiments in the Chesapeake Bay with a powerful searchlight was forty feet. In Long Island Sound one can seldom see over fifteen feet, and after storms, when sediment is carried into the Sound, sometimes it is difficult to see over three or four feet. I have been down on muddy bottom at a depth of one hundred feet and could not see my hand held close to my face. At a depth of one hundred and twenty-five feet in the Baltic on sandy bottom I was able to see twenty-five feet. This was about eight miles off shore, opposite Libau, Russia. In the English Channel the frequent storms stir up so much sediment that it is seldom possible to see over fifteen feet, while in the Mediterranean and our Southern waters near the Florida coast, near Nassau, and in the Caribbean Sea, it is possible at times to see seventy-five or even one hundred feet. Now there are means available to the submarine to enable it to lie at rest submerged at depths exceeding one hundred feet, and yet have a full view of surface ships and also to scan the heavens, therefore I would say that aeroplanes and dirigibles will prove ineffective against submarines fitted with revolvable turrets, high-angle firing guns, or where they may be operating in clear water exceeding one hundred feet in depth or in shallow water where the sediment held in suspension is in sufficient quantity to prevent discovery. Aviators with whom I have discussed this problem tell me they can seldom detect objects lying on the bottom, even in comparatively shallow water.