light-weight internal-combustion engines which practically all designing engineers have failed to grasp. Otherwise, engineers of all nationalities would not have failed to the extent they have; and I do not believe that there is a submarine engine in service to-day which has fully met the expectations of its designers and builders.

It is unfortunate for the engineering profession that government policy will not permit of a full disclosure of the defects of engines and other equipment in government-owned vessels. Were a frank disclosure made, other inventors and engineers would, in all probability, take up the problems and they might the sooner be solved.

All the earlier submarines were equipped with engines which used gasolene (petrol) as a fuel, but the gas from this fuel, when mixed with a proper proportion of air, is highly explosive. A number of serious explosions occurred in submarines due to this gas escaping from leaky tanks, pipings, or valves. Some of them were accompanied by loss of life. The most disastrous was that on board the Italian submarine Foca, in which it is reported that twenty-three men were killed. Therefore, several years ago, all governments demanded the installation of engines using a non-explosive fuel; and builders then turned to the "Diesel" engine as offering a solution of the problem.

As early as 1905 I had anticipated that such a demand would ultimately be made, so during that year I built, in Berlin, Germany, an experimental double-acting heavy-oil engine; but unfortunately the engineer in charge of the work was taken ill and eventually died. This engine was later completed and showed great flexibility in its control and in reversing. It, however, has never been put on a manufacturing basis.

In the meantime, others took up the work of developing the heavy oil Diesel engine for submarines. The first of the Diesel type engines to be installed in a submarine were built by a well-known French firm of engine builders. As we were then in the market for heavy-oil submarine engines, plans of these engines were submitted to me, but I found it impossible to install them in any boat we then had under construction, owing to their size and weight. I have been advised that engines of this design were installed in some of the French submarine boats. I have also been informed that the shock and vibrations produced by them were such as to cause the rivets in the boats to loosen, and this started the vessels to leaking so badly that it was found necessary to take them out. These engines differed only slightly from the vertical Diesel land engine.

The engine is the most important element in the submarine. Without this it is impossible to make long surface runs, and in the event of its disablement it is impossible to charge the storage batteries to enable the submarine to function submerged, which is, of course, what she is built for doing.

I think the demand for increased speed has come too rapidly. It is more important to have reliability than speed. The criticisms which have been made regarding United States submarines, if traced to their source, may be found to be justified so far as they apply to the engines, but the Navy Department cannot be held responsible, and neither can the designers of submarines. They have both searched the world's markets and secured the best that could be purchased. All naval departments were undoubtedly right when they decided to abandon the gasolene (petrol) engine and substitute therefor the heavy-oil engine. Eventually a successful heavy-oil engine will be produced.

STORAGE BATTERY CELL

A SUBMARINE CELL COMPLETELY ASSEMBLED READY FOR INSTALLATION

Storage batteries as used in modern submarines have been especially developed to meet the special needs of submarine-boat service. The requirements for this service are much more severe than those for any other service to which the storage battery has been applied. The batteries as first introduced in submarines were entirely too frail to stand up to their work, and the gases given off from them while being charged were the cause of much distress and danger to the crew, and have been in some cases responsible for the loss of both vessel and crew.

The Diesel engine, weighing practically five hundred pounds or more per horsepower, has functioned satisfactorily in land installations and has come into very general use, especially in Germany, but when the attempt was made to change this slow-speed engine of five hundred pounds per horsepower into high-speed engines of approximately fifty pounds per horsepower, all designers "fell down." It was but natural that naval authorities throughout the world should call for increased speed; they cannot be criticised for that, as it is a desirable thing, but experience has shown that they called for it too early in the game.

The expense of the development of a new type of motive power, such as the high-speed, heavy-oil-burning engine, for use in vessels whose prime purpose is to preserve the autonomy of the country, should be borne by the government rather than by individuals or private corporations. Millions of dollars have been expended in the development work of engines, but, although vast improvements are now in progress, the successful engine is not yet on the market.

Dr. Diesel has stated that he worked seven years before he succeeded in getting his first engine to make one complete revolution. Governments and the people must therefore content themselves to accept what they can get in a heavy-oil engine, imperfect though it may be, until such time as a satisfactory engine is evolved, built, and tested out under service conditions.

Storage Batteries.—It is impossible in a book of this character to go into much detail regarding the development of the storage battery. There have been two types in general use. They are both lead batteries, one known as the Planté type, in which metallic lead is used to form both the positive and negative plates. The other type employs what is commonly known as pasted plates, in which various compositions of materials are worked up into a paste and forced into metallic grids to form the positive and negative plates. The pasted type has greater capacity per pound of material used, but much shorter life.

In both of these batteries sulphuric acid solutions are used as the excitant between the elements. In charging, hydrogen gas is given off in the form of bubbles, the skin of the bubbles being composed of sulphuric acid solution. These bubbles, when taken in one's lungs, are very irritating, and if they collect in any quantity, or break up and allow the hydrogen gas to mix with the air, there is always danger of creating an explosive mixture within the hull of the vessel or in the battery tanks, which a spark would set off at any time.

The best method of installing batteries on a submarine boat is to have them isolated from the living quarters of the vessel in separate watertight compartments. The elements of the battery should be contained in non-metallic containers and sealed to prevent spilling of the electrolyte under excessive rolling or pitching of the vessel. Means should be provided to discharge the hydrogen gases from the boat as rapidly as formed. Special care should be taken to prevent leakages between the adjacent cells. Circulation of air to keep the cells dry is the best means of preventing this.

Mr. Edison has been working for a number of years on a storage battery suitable for submarine work, and it has recently been stated that he has finally solved the problem of producing a battery that will stand up longer than the lead type of battery, and that it has the further advantage in that it will not give off chlorine gas in case salt water should get into the cells. It should, however, be contained in a separate compartment, which should be ventilated during the charging period, as I understand the Edison battery gives off hydrogen gas the same as the lead batteries. Chlorine gas, as given off from the lead battery when salt water has got into it, has undoubtedly caused the loss of some lives. Mr. Edison claims that his battery, when immersed, will not give off poisonous gases of any kind.

METHOD OF CONTROL IN DIVING TYPE BOATS

Horizontal rudder set down aft inclines the vessel down by the bow, in which condition, with only a small reserve of buoyancy, she will "dive." When she reaches the desired depth a lesser inclination of the diving rudder is supposed to reduce her angle of inclination sufficiently so that the pressure on the top of her hull will offset the tendency to rise due to her positive buoyancy. To be successful there must be no movable ballast, and variable stream line effect requires expert manipulation of the diving rudder.

Depth Control.—Practically all modern submarines use hydroplanes with a horizontal rudder for the control of depth when under way. Hydroplanes might be said to correspond to the side fins of a fish. They are substantially flat vanes that extend from either side of the vessel. They are set on shafts that may be partially rotated by mechanism in control of a man within the vessel. They readily control the depth of the vessel with a certain amount of either positive or negative buoyancy. For instance, submarines are usually submerged with a small amount of positive buoyancy. If a vessel has positive buoyancy she will float. We have seen that in a surface condition the five-hundred-ton submarine has about one hundred and twenty-five tons of positive buoyancy.

METHOD OF CONTROLLING HYDROPLANE BOATS

Showing a proper arrangement of hydroplanes and horizontal rudders. C B represents the centre of buoyancy of the vessel when submerged. G represents centre of gravity, which lies directly beneath centre of buoyancy. Now if hydroplanes are located at equal distances fore and aft their up or down pull is always balanced and does not cause the vessel to dive or broach, but holds her to a level keel. If stream line pull tends to upset this level keel, horizontal rudders may be used to correct it.

Now to prepare the vessel for a submerged run, we admit, say, one hundred and twenty-four tons of water; the positive buoyancy is then reduced to one ton. Now if the forward edges of the hydroplanes are inclined downward (see diagram), and the vessel is given headway, the pressure of the water on top of the inclined hydroplanes, combined with the tendency for a vacuum to form under the planes, will overcome the one ton of positive buoyancy and will pull the vessel bodily under the water. When the desired depth is reached the operator sets the inclination of the hydroplanes so as to just balance the upward pull of the one ton of positive buoyancy, and the vessel proceeds at the desired depth. On modern boats the control of depth is most remarkable; it is very common for submarines to make continuous runs of several hours' duration without varying their depth more than a couple of feet. When the headway or motive force of the submarine is stopped, if she has reserved some positive buoyancy she will come to the surface. If she has negative buoyancy she will sink, but while under way with as much as a ton of positive or negative buoyancy the hydroplanes will absolutely control the depth of the vessel.

HOW HYDROPLANES CONTROL DEPTH OF SUBMERSION

The vessel being "under way" in the course of the arrow, the water contacting against the upper surface of the hydroplanes, as in the upper view, its course is thus diverted and adds weight to the upper surface of the planes. There is also a tendency to form a vacuum under the plane. Both these forces tend to overcome the positive buoyancy of the boat and force her under water and on a level keel if these forces are properly distributed fore and aft of the centre of buoyancy and gravity of the vessel.

Action of the Hydroplanes.—The diagrams are intended to demonstrate how it is that the Lake and other hydroplane boats can be so easily held at a predetermined depth and controlled vertically on an even keel.

The hydroplanes are symmetrically disposed on two sides of the vessel. They should be equal distance forward and aft of amidships. This symmetrical disposition, with equal forces acting on each hydroplane, compels the boat either to rise or sink on an even keel, depending upon which face of the hydroplanes is presented to the passing water during the boat's progress.

In the upper diagram the entering edges of the hydroplanes are inclined downward, and the force of the passing stream lines strikes upon the upper face of the blades. This exerts a downward force which causes the boat to sink, as indicated by the arrows marked "A, A." The opposite of this takes place when the forward ends of the hydroplanes are lifted. This brings the force of the stream lines against the under side of the hydroplanes, and the resultant is a lifting impulse in the direction of the line of least resistance, which is here indicated by the arrows marked "B, B." It is the lifting force so applied that makes it possible to raise hydroplane boats from the bottom even when having considerable negative buoyancy.

ON PICKET DUTY

This is a field of service to which the anchoring weights and the diving compartment of the Lake boats lend themselves conjointly with especial fitness. The illustration represents a submarine doing picket duty on an offshore station. A junction box is placed in a known locality with telephone or telegraph cables leading therefrom to the shore. The submarine, having taken her position on the surface, lowers her anchoring weights, reduces her reserve buoyancy to the desired extent, and then draws herself down to the bottom by winding in again on the cables connecting with the anchoring weights. Having reached the bottom, the diving door is opened and a diver passes out and makes the necessary connections between that junction box and the instruments in the boat.

Holding Depth When Not Under Way.—If it is desired to bring the boat to rest while submerged, but when no motive force is being used, other methods must be used than that just described. One method is to have an anchor or anchors to hold the