as full of machinery as an ordinary watch case, and every square inch of space is utilized to the utmost degree. None of this can be given up to any additional gadget without taking it away from something else.

SAFETY WEIGHTS OR DROP KEELS

One of the earliest methods of submarine salvage was the use of the so-called "safety weights," which consisted of huge blocks of iron or lead so attached to the bottom of the submarine that they could be released from the inside. The purpose of this was to decrease very rapidly the specific weight of the submarine and permit it to rise to the surface. Such weights were fairly regularly employed up to about the time of the World War, but the recent trend of opinion is against their use. In the first place, it has been found that the working of this device is neither rapid nor reliable enough for practical purposes. In the next place, the additional load reduces the speed of the submarine and its cruising radius to such an extent as to affect very materially the military value of the device. Finally, with the great increase in the size of submarines the weights that could have been used would have had to be inordinately large and, moreover, would have complicated the important problem of balancing when submerged. On the whole, therefore, the present tendency in design is to dispense with their use.

In one instance during the World War the drop keel was accidently knocked off an English submarine by contact with the sea bottom. The vessel was unable to submerge after the accident and ran the danger of being sunk by the enemy, getting back to England by mere fortune. A step in the direction of abandoning this scheme was the adoption of safety tanks. These tanks were filled with water, thus providing an extra weight, and when necessary could be very quickly emptied by introducing very high-pressure air carried for this purpose in special cylinders.

DETACHABLE CHAMBERS

The next device from which great things were expected was the detachable chamber. The idea was to provide in the hull of the submarine small compartments with double doors working something like the Servidor device used in hotels. Double doors were to be provided so that a person could pass into this detachable chamber, close the doors after him, have the chamber detached from the submarine, and float up to the surface. One of the suggestions was to make the entire conning tower act as such a chamber, so that in case of necessity the whole crew of the submarine might save themselves in this way. The problem of designing such a device so that it will withstand when detached the considerable pressures met at substantial depths is not an easy one. Moreover, with the present large submarines carrying a crew of some 85 perople, the device would have to be of a very considerable size. The question of placing these detachable chambers is also not an easy one. If they were located inside the hull they would occupy most valuable space, and space is what the designer of a submarine can least spare. If the chambers were located outside the hull, somewhat like warts on a frog's back, they would materially reduce the submerged speed of the vessel.

DIVING SUITS

It has been suggested many times-but not by submarine designers-that diving suits be provided for the crew, the idea being that in case of accident the crew could don these suits, open doors, and serenely walk out on to the ocean floor. The trouble with this scheme is, first, that in case of an accident, particularly where the hull is ripped open, there is seldom time for the rather elaborate operation of donning a diving suit. Next, not many men employed on a submarine are physically suited for work at substantial depths in an ordinary diving suit. On the other hand, however, in several European navies the so-called "oxylite" masks are carried. These masks have a chemical which is capable of absorbing moisture from the human breath and evolving oxygen in proportion thereto, so that a man can live in an oxylite mask for as long as three-quarters of an hour without breathing any ouside air.

The main value of these masks is in case sea water should accidentally penetrate into the storage batteries. Because of the reaction between the sodium and magnesium chloride in sea water and the sulphuric acid in the batteries, such an accident would result in the evolution of chlorine. Should this happen when the submarine was submerged, time would be needed to bring the vessel to the

surface and either ventilate it thoroughly or permit the crew to get outside For such a purpose masks of the oxylite type are quite valuable, and being comparatively light and small they are not in the way.

THE EXTENSIBLE TUBE

This device has been suggested on numerous occasions, the idea being to provide a tube of a diameter sufficient for a man of ordinary girth to pass through. This tube is supposed to be collapsed under ordinary conditions, somewhat like a traveler's aluminum drinking cup. In case of necessity it is to be extended so as to reach the surface and thus provide a means of egress for men trapped in a submarine. The device has never been adopted in practice by any navy, and the reasons for this are fairly obvious. Such a tube would have to be at least 25 inches in diameter. For a hollow tube to withstand water pressure at a depth of, say, 300 feet, it would have to be made very strong, particularly at the joints, which means that it would have to be quite heavy. It would occupy a lot of room, require quite an elaborate arrangement for extending it, and then would provide egress only to men trapped in the one compartment with which the tube communicated.

SAFETY TANKS

All submarines of the United States Navy are fitted with an automatic device which may be set to operate at a predetermined depth. Several different types of valves have been used, all of which operate on the same principle; i. e., the unbalancing of forces previously in equilibrium by sea pressure due to the depth of submergence. The tripping of such a valve opens the 100-pound air line to one or more of the main ballast tanks, usually forward of amidships, and allows air to be blown into the tank, forcing the water out through the Kingston valve, and thereby bringing the boat to the surface. These valves are not of an automatic repeating type, but require to be reset by hand after each operation. Valves of this type have generally proved satisfactory, being capable of arresting the descent of the vessel to within 5 feet of the intended depth, and criticism mainly has been directed to the capacity of the reducing valve which supplies air from the 100-pound line. No standard valve has been adopted. Two varieties have been installed on contract-built submarines, both of which are covered by United States patents. A special type of automatic valve has been designed by the Portsmouth yard and installed on the "S" vessels built by that yard, but has not been thoroughly tested as yet. Automatic control of the diving planes has been suggested and has been considered in a tentative way at various times, but no definite action along these lines has been taken, as it is believed that the complications involved would not be warranted by the advantage gained. The practicability of providing automatic arrangements for controlling the regulating or adjusting pump has been investigated, but in view of the complications involved it is not believed that the arrangement is practicable or would serve any useful purpose.

SIGNALING BUOYS

Many of the European submarines are equipped with signaling buoys which in case of accident can be released by the submarine and will indicate its position. In the German Navy, for example, these buoys are equipped with telephones, and at times attempts have been made to equip them at night with flares and in the daytime with smoke or sounding devices. These buoys were formerly quite extensively used in the American Navy, but of late have been discarded. The reason for this appears to be to be the possibility that in war time the concussion produced by depth bombs might release the buoy and thus indicate the position of the submarine to the enemy. It would seem to be quite feasible to use these buoys in peace time, and either batten them down or cut them off completely in war time.

If properly used and equipped these buoys constitute a valuable auxiliary, in particular by indicating immediately the location of the submarine and possibly giving information as to the condition of the vessel, the condition of the crew, and the degree of necessity for prompt action. The design of these buoys is, however, as yet in a very crude state, and no facilities are provided for the men in all of the water-tight compartments to communicate with the outside world by the telephone apparatus inclosed in the buoy. It may be stated in this connection that the whole subject of submarine safety devices is in an inchoate

state, and that even where such devices are used their design is usually quite crude and lacking in that careful working out which characterizes safety devices in civilian engineering.

With

This matter has been discussed with some of the officers of the Navy Department, who state that signaling buoys are not really necessary any longer. the present listening devices the submarine can make its presence known quite easily in various ways and can be located without any trouble, provided some one is alive inside who can send out the information. If everyone were killed in an accident, the marking buoys would not operate anyway.

WATER-TIGHT COMPARTMENTS

In case of partial failure of the hull through collision or otherwise, water-tight doors dividing the submarine into several independent compartments may prove to be the means of saving the lives of at least part of the crew. It is in this way, for example, that the lives of the men of the German submarine U-3 were saved, and those on the American S-4 prolonged.

The installation of water-tight partitions and doors is a well-known naval device, and its reliability of design has been fully established in the past.

In the American Navy the bulkheads making water-tight compartments are considered to be one of the most important provisions for safety on submarines. It is because of their presence that the lives of men on the O-5, S-48, and S-5 were saved. The engineering features involved in the design of the water-tight bulkheads are very interesting, and are being given the most serious consideration by the Navy. It should be realized in this connection that the big modern submarines are built to operate at depths in excess of 300 feet, which is equivalent to a pressure of about 145 pounds to the square inch. The bulkhead has to be built actually much stronger than even the hull, because while the pressure on the hull is determined by the 2TR relation, that on the bulkhead, should the water come in, is determined by the R2 relation. The modern bulkhead is therefore not a diaphragm structure with a door cut through it as one would imagine offhand, but a system consisting of very strong ribs with inverted dished partitions between them, and altogether represents an extremely strong structure.

EXTERNAL MEANS OF SALVAGE

All the foregoing devices may be classed as internal means of salvage by which the men in a submarine in case of accident can take care of themselves. Assuming, however, that this proves to be impossible, or that the question is not so much the saving of life as the recovery of the sunken vessel, we come to external means. These may be classified into two groups-first, those for the saving of life, and second, those for the salvage of equipment. In war time, under certain conditions, the order of importance is reversed, the equipment being considered more valuable than the few lives which it may contain.

AIR SUPPLY TO THE SUBMARINE

Only recently has this problem been thoroughly studied. There are two views as to how it should be done. One way is to supply air to the general air system, which includes the submergence tanks. The piping is so arranged that under ordinary conditions air pumped from outside will be delivered to all compartments. This may not happen, however, if the submarine has been seriously damaged as, for example, was the case with the S-4. The other way is to provide proper valve connections so that air can be admitted to individual compartments even when the general air system is injured. The former system has been adopted on American submarines. As a makeshift, air can be supplied to some compartments, as, for example, through the listening tubes, provided the proper valves are opened from the inside, and provided proper connections are either available or have been made for attaching the air hose. It does not appear clear why both systems should be used simultaneously, and it would appear perfectly feasible to change somewhat the piping arrangements, possibly by providing two-way valves, so that the system could be used either as a single system or for supplying individual compartments.

LIFTING MEANS

In the event that the injury to the submarine is of such a character that there is no way for it to rise to the surface of itself, even with the main tanks emptied of water, the thing to do is to raise it by outside means. There are only two

ways available: One is to attach to the submarine additional tanks, force the water out of them, and thus float the vessel; the other is to attach chains or wire ropes directly to the submarine and hoist it by brute force. In either event the operation falls into two stages: (1) Attaching lifting pontoons or hoisting chains to the submarine; and (2) putting through the hoisting operation itself. When plenty of time is available the operation is comparatively simple, provided, of course, that the submarine lies at a depth at which diving operations can be carried out without extreme difficulty. Where sufficient time is not available, those who are going to carry out the raising operation will sincerely appreciate any provision for doing the work as quickly as possible. It may be mentioned in this connection that time may not be available for two reasons. In the first place, men yet alive may be caught in the sunken vessel and the highest possible speed of operation may be needed to preserve their lives. In the second place, weather conditions may be such as to afford only a limited time in which to do the job. A combination of these two conditions was present, for example, in the initial salvage operation of the S-4.

MEANS OF ATTACHING CHAINS OR PONTOON TO A SUBMARINE

Any engineer who has had experience with crane operation or derrick work in construction knows the great difference between raising a heavy piece, so designed that it can be conveniently held by the crane hooks or chains, and doing the same job with perhaps a much lighter piece of such a shape that one has to use special inguenuity to hold it and is then perhaps not quite certain of being able to do so. While every designer of submarines knows that because of its very character of operation it is apt to get into trouble, out of which it will have to be pulled by raising, still the provisions for carrying out this operation are anything but ample. The most obvious way to assist in the raising operation is to do with the submarine what is, for example, done with a ladle or ingot mold in a steel mill, i. e., provide it with either bosses or eyes to which hooks or chain loops can be engaged. In fact, the Navy has been blamed by some Congressmen for not having done so in the case of the S-4. However, this question of hooks or bosses is more involved than appears on the surface. The early submarines were quite frequently provided with eyes riveted on the hull. Those vessels, however, were comparatively small and the load on each eye therefore quite light. With large modern submarines a rather different situation presents itself.

It should be remembered in this connection that the stress is not applied evenly to the eyes in lifting a submarine. A crane operator lifting a foundry ladle can more or less control the stress on the crane hook by pulling it up slower or faster. He is, however, operating from a perfectly fixed base, the crane bridge. The salvage vessels, on the other hand, when raising a sunken ship have no such fixed base, but on the contrary are supported by that most restless element, the ocean, with the result that the stress is either half eased off or suddenly applied with a powerful jerk. The strength of the hook or eye on a submarine is no greater than the strength of the rivets or the weld that holds it to the hull, or the strength of the hull itself. A brief calculation will show that if it were attempted to raise a submarine of the size of the S-4 by a few hooks or eyes welded or riveted on to it, the chances are that the hull would be ripped apart or the hooks torn away.

Of course, the reply to this will be, why have a few hooks and not a multiplicity of them? Here again the trouble lies with the lack of a fixed base. If we were to hoist a load from a crane bridge, it would be a comparatively easy proposition to provide, if necessary (and it is seldom necessary), a multiplicity of chains and arrange them in such a manner that the load would be easily distributed among all the chains. If, however, the same thing were attempted in marine salvage operations without some very special equipment, the chances are that the load would alternately vary and be carried at all times by some two or four sets of eyes, at least to the extent of 75 per cent, so that the multiplicity of these eyes would not materially help in relieving the stresses on the hull.

The French submarine designer Laubeuf proposed, however, a modification of this device which appears to be of sufficient importance to deserve serious consideration. What Laubeuf suggested is to attach wide bands of metal to the submarine by riveting or welding and to have the hooks or eyes for the accommodation of the lifting chains made a part of these bands. In this way the hoisting stress would be distributed over a comparatively wide area of the hull, and with proper design and distribution of these bands it would appear possible

to give these hooks or eyes such proportions and such a distribution as would assist materially in accelerating the raising operations.

Since Laubeuf's time a new development has taken place which may help in this connection. All that Laubeuf had at his disposal were carbon-steel bands with a tensile strength of some 100,000 pounds. To-day it would be possible to make these bands in the form of chrome-nickel steel forgings with a tensile strength considerably in excess of 200,000 pounds and a permissible emergency loading of some 175,000 pounds per square inch. Under these conditions such bands with the concomitant hooks or eyes would appear to be well deserving of serious consideration.

It should be borne in mind that the provision of bands will require in the first place possible changes in the design of the longitudinal frame members of the submarine, with the idea of giving them additional stiffness. This is a more difficult problem than a layman or engineer who has not had anything to do with submarine design realizes. The other point to which very serious consideration must be given is such stream-lining of these bands as will not materially reduce the submarine speed, particularly its surface speed, the underwater speed being too low to be materially affected by the presence of the bands.

ATTACHING CHAINS TO SUBMARINES

Obviously, before a submarine can be lifted, chains have to be passed properly around it. It may be somewhat surprising to an engineer to learn that no provision for doing this quickly and conveniently is made on any of the submarines of any country. The submarine may be lying in the most inconvenient position, on a rocky bottom or-which is equally bad if not worse-partly sunken in mud, as is the case with the S-4. When this happens tunnels have to be laboriously blown under the submarine hull to pass the chains or hoisting ropes. This means increasingly hard and dangerous work on the part of the divers, possible interruptions by weather, with destruction of what has been already done on the bottom, and furthermore no certainty that the chains will be placed where they should be. To an engineer it would appear that a very simple provision could be made to take care of this situation. This could take the form of welding on to the submarine hull a few thin channel-shaped pieces so arranged that they could be opened in places and serve as guides for the hoisting chains. It would be a simple matter to locate in these channels a slender wire rope with proper provision for attaching the chain at one end and passing it around the submarine by pulling on the rope from the other side. The operation in principle would not differ from the way in which heavy cables are passed underground by the telephone companies. Proper thought should be given to making these channels of such a shape as not to reduce the surface speed of the submarine, but otherwise the device is extremely simple. There is one objection to it, however, and that is that these guide channels, being made of fairly thin metal, would be apt to get bent or twisted. Should this happen the submarine would be no worse off than it would be without them, and there is really no reason why they could not be made strong enough to withstand ordinary bumping.

STATEMENT OF MILLER REESE HUTCHISON, PH. D.

Senator ODDIE. Doctor Hutchison, will you please state for the record your occupation?

Doctor HUTCHISON. Business engineer; business executive; specialty, analysis and common sense; I know something about submarines; I have had direct contact as observer; and I will be glad to answer any questions that I can. If I do not know I will tell you so. Senator ODDIE. Are you a member of the Naval Consulting Board? Doctor HUTCHISON. Yes, sir.

Senator ODDIE. How long have you been a member of the Naval Consulting Board?

Doctor HUTCHISON. Since its inception.

Senator ODDIE. Were you one of its originators?

Doctor HUTCHISON. Yes, sir.

Senator ODDIE. Are you connected with Mr. Thomas A. Edison?