Any technical description of German mines would be out of place here; but it may be said that generally they approximate to a spherical shape, and are provided with projecting “horns,” almost in the shape of drumsticks, concussion with which is calculated to break a small phial within, whose contents cause the detonation of the enormous charge of T.N.T. explosive. Each mine is provided with a sinker, which drops to the bottom, and is attached to the mine by a cable or sounding-line paid out by special mechanism to any desired length, whereby the mine may be kept at the intended depth below the surface. There are other types of mines, and in particular one of cylindrical form, containing a prodigious quantity of explosive and capable of the widest destruction. This has probably been used only in special situations. The ordinary mines can be laid with great rapidity by a specially fitted mine-layer, provided with rotary gear, bringing mine after mine along a special track to the dropping position. The drifting mines which the Germans at the very beginning of the war set afloat in the main trade route from America to Liverpool, _viâ_ the North of Ireland, can be laid with still greater rapidity. When mine-laying in British waters by surface boats was made extremely risky, or almost impossible, the Germans resorted to the employment of submarine mine-layers, one of which was exhibited in the Thames. Vessels of this class, so far as they are known, probably carry a maximum of twelve big mines in six shoots or air-locks, the lower mine in each shoot being released by means of a lever, after which the other drops into its place, ready to be let go in the same way. The boat exhibited in London and elsewhere was of a rough, rudimentary character, indifferently built, and her speed was probably not more than six or eight knots. Undoubtedly many of the submarine mine-layers are of better type. They are constantly at work especially on the east coast of England, and some losses have resulted; but the effect of their operations is nearly always overcome by the means adopted by the Navy.