The menace of the German sea-mine remains the greatest war danger to which the lightships are exposed. Zeppelin and seaplane pay visits to the coastal waters, but the sea is wide for a chance missile from the air, and no great success has attended their bombing efforts. But the enemy mine has no instant aim. Full-charged and deadly, its activity is not confined--as the British mine is--to the area of the mooring. Their minelayers, creeping in to the fairways in cloak of the darkness, are anxious to settle their cargo of high explosive as quickly as possible. Not all of the mines they sow hold to the hastily slipped 'sinkers' till disaster to our shipping or the untiring search of the minesweepers reveals their presence. Many break adrift and surge in the tideways, moving as the set of the current takes them. Vessels under way, by keen look-out and ready helm, can sight and avoid the drifting spheres, but the lightships have no power to steer clear. Moored on the offset of a shoal or sandbank (their position, indeed, a guide to the minelayer), their broad bows offer contact to all flotsam that comes down on swirl of the tide. The authorities were unwilling to expose their men to a danger that could not be evaded, however gallant the shipmen or skilled their seamanship. It was not a seagoing risk that could be met; no adequate protection consistent with the lightship's mission could be devised. As the submarine war became intensified, the more distant vessels were withdrawn; new routes were set to divert shipping from the outer passages; only those floating sea-marks are now maintained whose removal would entail disaster to the traffic that passes by night and day.