The Tuck also comes from America. It is of iron, cigar-shaped, thirty feet long and six feet in diameter. It is submerged by means of a horizontal rudder in the stern and a horizontal propeller acting vertically amidships beneath the boat. It is driven by electricity, supplied from storage batteries packed closely in the bows. Compressed air is carried in reservoirs, but a supply is usually obtained when the boat is not far from the surface, by means of an iron pipe twenty feet long, which usually lies on deck, but which can be raised to an upright position by gearing from within. The top then rises above the surface of the water, and by opening a valve in the foot and attaching a pump, fresh air is drawn into the interior. The crew need not exceed three men.
Section of the Goubet Submarine Boat.
The Goubet class are of iron, sixteen feet long, three feet wide, and about six feet deep. The motive power is a Siemens motor driven by storage batteries. Fifty of these boats were purchased by the Russian government. They have no rudder, but a universal joint in the screw shaft permits of the screw being moved through an arc of ninety degrees. The torpedo is carried outside the boat, secured by a catch worked from inside. On arriving under the enemy, the torpedo is released, and striking the ship's bottom, is held there by spikes. The boat then withdraws, unreeling a connecting wire; and when at a safe distance, fires. The absence of a rudder, however, causes erratic steering, and the spikes with which the torpedo is fitted might fail to stick in steel-bottomed ships.
Submarine boats cannot be driven under water at a speed exceeding six knots. If driven beyond, they are inclined to dive, and in deep water, before the corrective forces against a dive have had time to act, might reach a depth where the pressure would drive in the sides or compress them to a sufficient extent to seriously reduce the displacement. In shallow water, the boat might be driven on to the bottom, and if it be clay, held there, an accident attended with fatal consequences in the case of one boat.
It is also difficult to direct the course of a submarine boat; and it is doubtful whether the advantage of not being seen counteracts the disadvantage of not being able to see. According to Mr Nordenfelt in a lecture on Submarine Boats, 'The mirror of the surface throws a strong light into the boat; you cannot see forward at all, and you cannot see far astern; it is as black as ink outside; you can only see a sort of segment.' This means that you cannot safely advance at a great speed under water. It is impossible to think of a submarine boat as a boat that actually manoeuvres and does its work under water. The boat should run awash, and you can then see where you are. When we consider, then, that a boat totally submerged cannot be driven over six knots, and cannot be properly directed; when we consider the speeds of seventeen and eighteen knots attained by modern battleships, we arrive at the conclusion that boats totally submerged are useless against modern battleships in motion. Running awash, they could be tackled by torpedo catchers and torpedo boats.
