Hundreds of British mine-layers are planting their deadly “eggs” by the thousands to blast German submarines from the seas and tighten the blockade of Europe. Pushed along tracks on the stern of a vessel, 300 big mines can be laid in one hour. Half the space in the mine heads is filled with explosives and firing batteries and the rest of the space is an air chamber for buoyancy. In this war the Royal Navy has far surpassed its mine-laying activities of World War I when a total of 128, - 652 mines were laid.