on the surface rather than submerged, although laying them submerged presented no particular difficulties except those of navigation. Mines were generally laid with the submarine traveling at full speed. The mine with its anchor and tracks, when released by the submarine, sinks to the bottom; upon reaching the bottom the hydrostatic pressure works on a small piston which in turn actuates a releasing device. When the mine is released the safety pin of the contact maker is withdrawn and the mine, from that point on, is armed. The mine continuing

HORN OF A GERMAN MINE.

to rise reaches a point about six to ten feet from the surface of the water, when the hydrostatic clamp gets in its dirty work and holds the mine securely. In case the hydrostatic gear fails the mine will float.

If the part of the cable on which the hydrostatic clamp is working accidentally be cut, the mine will start to rise suddenly, whereupon a mechanical clamp on the other part of the cable engages and holds it fast.

From the above it will be seen that the mine is held to the anchor by two parts of the cable in the form of a single purchase, necessitating-before the mine will float-that both cables be cut. The fact that German mines were moored with a double cable instead of a single made necessary the invention of some form of explosive shears in preference to a mechanical shears,

in order that the chances of getting the mines would be increased by that much.

In the early days of the war when mechanical shears were used there were but four on each arm of the V. The mechanical shears could work on but one cable. They were supposed to be automatic in their action, but the device at first was a clumsy affair and very heavy. The explosive shears carry two knives and a hook, so that in case the knives fail the hook is still there to catch the mine cable. It frequently happened before the explosive shears were perfected that they would fail to function and a mine would be dragged along. The anchor being dragged along as well would bounce from rock to rock over the bottom, finally shearing itself, whereupon the mine might float and easily be sunk.

Again, when the shears failed to function a mine with its anchor might be dragged up close under the vessel, in which case the sweeper would head for the nearest sandy beach, constantly keeping the mine in view but well astern.

Upon arrival in a satisfactory anchorage the dragger would then release the sweeping gear at the apex of the V and permit the entire apparatus to sink. The floats at the kite end being on the surface would be sufficient to mark the spot where the drag and mine was located. The vessel would then proceed to a safe anchorage and at once send all hands of the crew that could be spared out with several hundred fathoms of line to haul the

Lead weight

Bridle

Rudder

Float

DEPTH PLATE AND FLOAT.

mine upon the beach where it could be either examined or destroyed, as desired.

In hauling the mine on the beach the float would first be hauled inshore. Next the kite, and as soon as the mine appeared above the surface of the water the long line would be manned and the mine hauled up on the beach. The antennæ or lead horns are the source of danger, because the bending of one of these horns would cause an electric current to be generated, resulting in the explosion of the mine.

If the mine is to be examined, the procedure should be about as follows: First, pull the contact maker out and insert a safety pin; next, unscrew the plate holding the contact maker. This

would expose the electric wires which can then be cut. As soon as the wires are cut out the mine is safe. Next remove the horns and lastly remove the primer. The mine can then be examined at will.

In case it is desired to explode a mine which has been brought up on the beach, two methods present themselves: One, to endeavor to explode it by rifle fire, shooting at the horns; second, to attach a line to the horns and endeavor to break one. Both methods have been used with success.

It is a remarkable fact that the French have examined a great many mines with very few casualties. To get an idea of the amount of force necessary to bend one of the leaden horns, it may be interesting to note that 20 men had all they could do to break one.

The personnel of the American sweepers consisted of less than 10 per cent of regular officers and less than 40 per cent of regular enlisted men. The ages vary from 18 to 56, the average age being somewhere in the vicinity of 23.

Any one thinking that it is a simple matter to train a ship's company in the gentle art of mine sweeping has many a disappointment ahead of him. However, with persistence and patience much can be accomplished.