Part 62

To understand this we must go back to the explanation of the five senses--sight, hearing, feeling, tasting and touching. Now, each of these senses has a special set of nerves through which the sensations received by each of the senses is communicated to the brain and, as a rule, these special nerves receive no sensations excepting those which occur in their own particular field of usefulness. The eye then has nerves of vision; the nose, nerves of smell; the ear, nerves of hearing; the mouth, nerves of taste, and the entire body nerves of touch. As we have seen then, these special nerves are susceptible of receiving impressions or sensations only in their particular field. But, if you should be able to rouse the nerves of smell in an entirely artificial way and give them a sensation, they might easily act very much as though they smelled something. We find this often in the nerves of touch when we think we feel something when we do not.

Now, when some one hits you in the eye, the nerves of vision are disturbed in such a way as to produce upon the brain the sensation of seeing light. In other words, you cannot affect the eye nerves without causing the sensation of light, and that is just what happens when some one hits you in the eye.

Experimental Boat, 1894.]

Built 1896-1897.]

The Story in a Submarine Boat

How Can a Ship Sail Under Water?

Up to a few years ago the stories we could tell about the ships that sail beneath the water were the creations of the minds of writers of fiction, like the author of “Twenty Thousand Leagues Under the Sea,” but to-day we can read of many actual trips beneath the water by the brave men who man our submarines. We never dreamed that the great story of Jules Verne would be realized in the little but very destructive ships of war which can be seen to-day in the naval ports of the nations of the world.

We might have had these submarines long ago but for the fact that the men who were trying to invent them would not give up the secrets which they had discovered. Many men in different parts of the world worked on this problem and each discovered one or more things which were valuable in working out a solution, and if they had all gotten together and compared notes between them they could have produced a submarine boat almost as good as those we have to-day.

How Does the Submarine Get Down Under the Surface?

The first essential in a vessel to enable it to navigate below the surface of the water is that it be made sufficiently strong to withstand the surrounding pressure of water, which increases at the rate of .43 of a pound for each foot of submergence.

A boat navigating at a depth of 100 feet would therefore have 43 pounds pressure per square inch of surface, or 6192 pounds for every square foot of surface. It will readily be seen, therefore, that the first essential is great strength. Therefore, the submarine boats are usually built circular in cross section with steel plating riveted to heavy framing, as that is the best form to resist external pressure. These boats are built for surface navigation as well, therefore they have a certain amount of buoyancy when navigating on the surface, the same as an ordinary surface vessel. When it is desired to submerge the vessel this buoyancy must be destroyed, so that the vessel will sink under the surface.

Now, the submerged displacement of a submarine vessel is its total volume, and, theoretically, a vessel may be put in equilibrium with the water which it displaces by admitting water ballast into compartments contained within the hull of the vessel, therefore, if a vessel whose total displacement submerged was 100 tons, the vessel and contents must weigh also 100 tons. If it weighed one ounce more than 100 tons it would sink to the bottom. If it weighed one ounce less than 100 tons it would float on the surface with a buoyancy of one ounce. If it weighed exactly 100 tons it would be in what submarine designers specify as being “in perfect equilibrium.”

It is possible to give a vessel a slight negative buoyancy to cause her to sink to, say, a depth of 50 feet and then pump out sufficient water to give her a perfect equilibrium, and thus cause her to remain at a fixed depth while at rest. In practice, however, this is seldom done. Most submarine boats navigate under the water with a positive buoyancy of from 200 to 1000 pounds and are either steered at the depth desired by a horizontal rudder placed in the stern of the vessel, or are held to the depth by hydroplanes, which hydroplanes correspond to the fins of a fish. They are flat, plane surfaces, extending out from either side of the vessel, and when the vessel has headway, if the forward ends of these planes are inclined downward, the resistance of the water acting upon the planes is sufficient to overcome the reserve of buoyancy and holds the vessel to the desired depth. If the vessel’s propeller is stopped, the boat, having positive buoyancy, will come to the surface.

By manipulating either the stern rudders or the hydroplanes, the vessel may be readily caused to either come nearer to the surface or go to a greater depth, as the change of angle will give a greater or less downpull to overcome the reserve of buoyancy.

The above description applies to navigating a vessel when between the surface of the water and the bottom.

Another type of vessel which is used for searching the bottom in locating wrecks, obtaining pearls, sponges, or shellfish, is provided with wheels. In this type of vessel the boat is given a slight negative buoyancy, sufficient to keep it on the bottom, and it is then propelled over the water bed on wheels, the same as an automobile is propelled about the streets. This type of vessel is also provided with a diver’s compartment, which is a compartment with a door opening outward from the bottom. If the operators in the boat wish to inspect the bottom, they go into this compartment and turn compressed air into the compartment until the air pressure equals the water pressure outside of the boat; i. e., if they were submerged at a depth of 100 feet they would introduce an air pressure of 43 pounds per square inch into the diving compartment. The door could then be opened and no water could come into the compartment, as the diving compartment would be virtually a diving bell. Divers can then readily leave the boat by putting on a diving suit and stepping out upon the bottom.

“PROTECTOR.” BUILT 1901-1902, BRIDGEPORT, CONN.

This was the pioneer Submarine Torpedo Boat of the level-keel type, and was built in Bridgeport in 1901-1902. It was shipped to St. Petersburg, Russia, during the Russian-Japanese war. From St. Petersburg it was shipped to Vladivostok, 6000 miles across Siberia, special cars being built for its transport.]

In neither condition is it necessary to have recourse to electrical propulsion--the boats can still be safely and speedily driven as here shown under their engines.]

THE “G-1” RECENTLY DELIVERED TO THE UNITED STATES GOVERNMENT.

The largest, fastest submarine in the United States and the most powerfully armed submarine torpedo boat in the world.

In addition to the usual fixed torpedo tubes arranged in the bow of the vessel, which requires the vessel herself to be trained, the (seal) “G-1” carries four torpedo tubes on her deck which may be trained while the vessel is submerged, in the same manner as a deck gun on a surface vessel is trained, and thus fired to either broadside, which gives many technical advantages.]

The commanding officer is at the periscope in the conning tower directing the course of the submarine through the periscope, which is a tube arranged with lenses and prisms which gives a view of the horizon and everything above the surface of the water, the same as if the observer in the submarine was himself above water. The steersman is shown just forward of the commanding officer and steers the vessel by compass under the direction of the commanding officer, the same as when navigating above the surface. In the larger type boats the steersman also has a periscope which enables him to see what is going on above the surface. Below decks two of the crew are shown loading a torpedo into the torpedo tube; each torpedo is charged with gun-cotton and will run under its own power over a mile and will explode on striking the enemy. The crew live in the compartment aft of the torpedo room. Aft of this is the engine room, in which are located powerful internal combustion engines for running on the surface and electric motors for running submerged. The electric motors are driven by storage batteries located under the living quarters. Wheels are shown housed in the keel, which may be lowered for navigating on the bottom in shallow water. A diving compartment in the bow permits divers to leave the vessel when on the bottom, to search for and cut or repair cables or to plant mines.]

A submarine running partly submerged with the conning tower hatch open, showing the remarkable steadiness of this type of boat in a semi-submerged condition, a thing no other craft could safely accomplish.]

AN ALL-SEEING EYE FOR THE SUBMARINE

Vision under water is limited to but a few yards at best, and hence a submarine boat, when submerged, would be as blind as a ship in a dense fog and would have to grope its way along guided only by chart and compass, were it not for a device known as a periscope, that reaches upward and projects out of the water, enabling the steersman to view his surroundings from the surface. Of course the height of the periscope limits the depth at which the craft may be safely sailed. Nor can the periscope tube be extended indefinitely, because the submarine must be capable of diving under a vessel when occasion demands. But when operating just under the surface, where it can see without being seen, the craft is in far greater danger of collision than vessels on the surface, because it must depend upon its own alertness and agility to keep out of the way of other boats. The latter can hardly be expected to notice the inconspicuous periscope tube projecting from the water in time to turn their great bulks out of the danger course.

The foregoing article describes the type of periscope now in common use on submarines and one of the engravings on this page clearly illustrates the principles of the instrument. A serious defect of this type of instrument is that the field of vision is too limited. The man at the wheel is able to see under normal conditions only that which lies immediately before the boat. It is true that he can turn the periscope about so as to look in other directions, but this, of course, involves considerable inconvenience. On at least two occasions has a submarine boat been run down by a vessel coming up behind it.

~SEEING IN ALL DIRECTIONS AT ONCE~