Submarine mine

“ You know, there are important fortifications there, because the Navy people expect, in wartime, to use Craven's Bay as a possibly important naval station and shelter for vessels that have to put in. Now, for some time the Army engineer officers have been perfecting a system of submarine mines for the bay. The engineers have a problem on hand as to whether an enemy's submarine boats could sneak into the bay and blow up the submarine mines before the Army woke up to the danger. ”

“ The submarine mine is primarily the defence of the weaker naval power, and therefore a fleet acting on the defensive, either temporarily or permanently, requires more mine-layers than mine-sweepers, but the reverse is naturally the case with a fleet acting on the offensive. Although this may be taken as a general rule, it does not imply that a strong naval power like Great Britain, whose policy is attack and not defence, needs no mines or mine-layers. On the contrary, the laying of counter mines is one of the ways of destroying an enemy’s mine-field ”

“ A submarine mine consists of an explosive charge inclosed in a water-tight case, and a firing device, the whole intended to be submerged in a waterway which it is desired to close against the passage of an enemy’s vessels. ”

“ A submarine mine of to-day consists of a mine case, shaped like a ball or egg, about one yard in diameter, mounted on an anchor in the form of an iron box about 30 inches square, connected by a wire rope mooring cable, about 3⁄8 inch in diameter. The mine case contains the charge of high explosive—300 pounds of TNT in our mines—and the firing mechanism. The combination stands about 5 feet high and weighs 1400 pounds. Four small car wheels on the anchor run on steel tracks, allowing the mines to be easily moved along the decks to the launching point. ”

“ Thus, if such a mine were to be used at all, we should have had to plant several layers, one under the other, down to a depth of about 250 feet, so that the submarine, at [Pg 250] whatever depth it might be sailing, would be likely to strike one of these obstructions. This required such a large number of mines as to render the whole project impossible. We Americans may take pride in the fact that it was an American who invented an entirely new type of mine and therefore solved this difficulty. ”

“ Linder?” drawled the visitor.
“Huh?” returned the Honorable William Linder, startled.
“Submarine mines,” explained the other., “Mines in the sea, if you wish words of one syllable.”
The lids of the Honorable Linder contracted.
“You’re in the wrong joint,” he said, “this ain’t the Naval College.”
“Thank you. A submarine mine is a very ingenious affair. I’ve recently been reading somewhat extensively on the subject. The main charge is some high explosive, usually of the dynamite type. Above it is a small jar of sulphuric acid. Teeth, working on levers, surround this jar. ”

“ While new and larger U-boats are sent abroad on the trade routes, special submarines, less encumbered by the stores and equipment that longer passages would demand, make frequent visits to the fairways to sow a freight of mines. No section of the channels holds sanctuary for the coaster. Close inshore, as in the offing, is all a danger area, open to the stealthy visits of the submarine minelayers. ”

“ In the absence of patrol vessels to drive them down, submarines would naturally run on the surface, and so the rows of upper level mines were made more numerous than those at deeper levels. The stroke of a mine is sudden and powerful, and while a vessel on the surface may survive it, to a submerged submarine it is usually fatal. All classes of vessels shy at a minefield, and that the Germans shared this aversion was shown by captured papers, which made it clear that the submarines dreaded nothing so much as mines. ”

“ Equipped with the "mine-evading" guards, they might even work their way into an enemy's harbor and plant mines under a vessel at anchor, or destroy shipping lying tied up at the docks. For defensive purposes a mine-laying submarine would be of great value, as it could readily plant mines, even under the guns of a powerful fleet, to protect its own entrances and harbors.
The submarine Protector, built in 1901 and 1902 at Bridgeport, Connecticut, was fitted with a diving compartment which corresponds to the mine-laying compartment of the 1905 design above referred to. ”

“ Frequent inspections of all articles of submarine mine equipment should be made, not only to check up the property, but also to determine the condition of all matériel, and especially to see if it has been affected by dampness. ”

“ But whether the submarine is used for mining its own or enemy harbors, the outstanding feature of its [121] work is that it does it all under water and therefore the operations cannot be seen by spying eyes.
As we said in Chapter III, the mines are stored in a compartment in the hull of the submarine and this can be shut off from the other compartments by a bulkhead door. It also has a hatch opening through the hull to the water outside, just as the door of a kitchen opens into the back yard. ”

“ Within signal-range or wireless call of the aërial scouts and their attendant ships are destroyer flotillas to give battle to the hostile submarines, while hundreds of trawlers and small steamers, fitted with special apparatus, are continually sweeping 11up the hundreds of submarine mines laid by the enemy’s vessels which are fitted to enable them to sow like seeds over the pathways of the sea these deadly perils to navigation. ”

“ A. A submarine mine is a ball-shaped iron case filled with high explosive. Several of these are planted across a channel and held below the surface of the water by heavy anchors. From each mine is run a single-core cable. All these cables join the wires of a multiple-core cable which runs to the "mining casemate." In this building are electrical devices for firing the mine either when it is struck by the enemy's ship (called "contact-firing,") or at the mine-commander's will ("observation-firing") . This firing is accomplished by sending an electric current through the cable to the mine. ”

“ The thing most astonishing to me about that experience was how a submerged submarine can thread its way through a mine field. For though the water is luminous and translucent one can hardly make out the black hull of the boat under the turret and a mine would have to be on top of you before you could see it. The men who watch for mines must have a sense for them as well as particularly powerful sight. ”

“ In small fields, of a few score or hundreds of mines, laid piecemeal by fixed marks, the mines in adjacent lines are usually “staggered,” so as to halve and block the opposite intervals, but in an open-sea minefield of immense area, far beyond sight of any marks and laid at 12 knots speed or faster, no such nicety is possible or necessary. The great Northern Barrage opposed from 6 to 10 lines of mines to a submarine on the surface and three to four lines more at whatever depth the submarine might think he could safely pass. Absolute impassability never was attained nor expected. ”

“ Both Germany and Austria have converted a large number of their merchantmen into mine-layers. England, in reply, has converted a large number of small steamers into mine-sweepers. Russia is a strong believer in explosive mines, and has strewn the gulfs of Finland and Riga with them. Japan, being on the offensive, is employing more mine-sweepers 175than layers. France has an elaborate system of submarine mine defence for all her important harbours, and maintains a small fleet at each base, known as the “defence mobile.” These vessels are all capable of both mine-laying and sweeping. ”

“ In the summer of 1861 he was appointed Chief of the “Naval Bureau of Coast, Harbor, and River Defense”, and began to plan the construction of submarine mines to be placed in the rivers and harbors of the South. These were to be exploded under enemy ships by electricity, and insulated wire was needed for this purpose. He accordingly sent a Richmond merchant to New York to secure a large quantity of such wire. The merchant failed in his mission, but Maury undismayed set about devising mines which could be exploded in a different way. ”

“ In Nov. mines were reintroduced for defence of harbours, and a special corps of Royal Marine submarine miners was started to manipulate them. By the end of 1914 some 2,000 mines had been laid in the southern part of the North Sea, which had a good effect in forcing neutral shipping to pass through the Downs, and for a time deterred enemy sub- marines from approaching the Channel. During 1915 a number of fields were laid in German waters and the minelaying squadron was greatly strengthened. ”

“ Men were busy at the stern of the ships watching the wooden kites that are made so as to catch the mines by the hawser that is slung between the two steamers. The slightest sign of a ball-like piece of steel in the sea and the dullness of sweeping is relieved, for then the skipper knows that he has unhooked one of the mines. Along came a submarine, flying the white ensign of the Royal Navy. The mine-sweepers realise that these men have no arm-chair job, and admire the commander and crew of the under-water boats accordingly. ”

“ It is very evident that if a diving boat can attain a speed of ten or twelve miles per hour, fire torpedoes at ships moving at full speed, and keep to sea for days together, her sphere of usefulness would be greatly extended. In fact, there is no insuperable objection to the employment of such vessels for coast defence and operations against ships. Submarine mines are not so effective against them as vessels on the surface, because they can pass them unobserved. They can enter a harbor that may be thoroughly defended, should it be necessary to destroy vessels inside the defences. ”

“ Some of the new features were the development of depth-charge throwers, the manufacture and use of fast coastal motor-boats for anti-submarine work, the production of mines of an improved type for use especially against submarines, very considerable developments in the use of minefields, especially deep minefields, including persistent mining in the Heligoland Bight and the laying of a complete minefield at varying depths in the Straits of Dover; also, after the United States entered the war, the laying of a very extensive minefield right across the northern part of the North Sea. ”

“ The French coast opposite Dover was also heavily mined. In the Dover area 212 mines were laid during the year (not including too off Dunkirk, 100 off Calais and 60 off Boulogne) , with a loss of two destroyers, five minesweeping trawlers and 20 steamers.
The unrestricted submarine warfare in 1917 was accompanied by an increase in submarine minelaying, and in the month of April 515 mines were swept up, considerably more than in any previous quarter. The reorganization of the naval staff led to considerable changes in the minesweeping service. ”

“ On being discharged into the sea they automatically adjust themselves to float about ten feet below the surface (according to tide) and are anchored to the bottom by means of a wire mooring rope attached to a heavy sinker. To describe here the mechanical details of all the different types of German submarine mines would occupy many pages with uninteresting technical formulæ. It is sufficient to say that they carried an explosive charge (200 to 400 lb. of T.N.T.) sufficient to blow to pieces vessels of several hundred tons and to seriously damage the largest warship. ”

“ The patrolling submarines were bombed constantly by enemy Zeppelins and seaplanes, but with little effect. To the submarine the mine was by far the greatest danger, and no doubt the depth charge too accounted for some of our casualties. But, as I have said, in nearly all cases when a submarine is lost, no one knows what has happened. She merely does not come back. The mine-laying of the Harwich submarines was chiefly directed against the enemy submarines, the mines being generally laid at about eight feet below the surface, so as to catch these craft while travelling on the surface. ”

“ Ten ships laden with high explosive, navigating in mine-swept channels, in submarine thoroughfares, and near minefields beyond sight of fixed marks—compactness of the minefield demanding that the layers steam as near together as safe—necessity for keeping together in fog, darkness, or submarine attack—these were the conditions governing our tactics. ”

“ A few quiet but searching experiments developed it into a mine of more promising effectiveness than any ever used before, especially against submarines. This gave the United States Navy the definite means to offer an anti-submarine barrage, on the German coast or elsewhere, and the result was the northern mine-barrage in the North Sea, stretching from the Orkneys 280 miles to Norway, which the Secretary of the Navy's annual report characterizes as "the outstanding anti-submarine offensive product of of the year." ”

“ The British mine was more complicated, and, instead of concentrating attention on the production of a good mine, efforts were wasted in an attempt to devise a combination of mines and nets which achieved little or nothing.
The ordinary minefield was usually laid so as to be about 10 to 15 ft. below the surface at low water, but the success of the submarine gave rise to the conception of deep minefields laid at about 60 to 1 50 ft. to intercept the submarines when submerged. The ordinary surface minelayers now began to be supplemented by submarines and destroyers ”

“ When Fernald came back with Dan Dalzell, Dave was still poring over the charts.
"From the rapid way in which German mines are being planted in these waters," Dave told his [152] brother officers, "I am satisfied that the enemy submarines do not usually go all the way back to the base port. I believe that the mine-layers are often met by other craft that supply them with mines, and that the submarine mine-layers return quickly to the job of planting mines. Now, the sea area in which the mines are planted leads me to feel certain that the mine-layers rest frequently on these three shoals." ”