g at low water.
Flotillas of trawlers and drifters for the hard and monotonous routine
sweeping on the important coastal trade routes. They comprised in all
several thousand ships engaged solely on this work.

At each important base there was a Port Minesweeping Officer (P.M.S.O.),
with one or more assistants, whose duty it was to administer, under the
command of the S.N.O., the fleets in the attached area, and to furnish
preliminary telegraphic and detailed reports to the Minesweeping Staff
at the Admiralty, who issued a confidential bi-monthly publication to
all commanding officers which was a veritable encyclopaedia of valuable
information regarding current operations, events and enemy tactics.
Attached to this department was a section of the Naval School of
Submarine Mining, Portsmouth, where all knotty problems were unravelled
and appliances devised to meet all kinds of emergencies.

Each unit of ships was under the command of a senior officer,
responsible for the operations of these vessels, and where big fleets
were engaged a special minesweeping officer was placed in supreme
command. Only by close co-ordination of effort from the staff at
Whitehall and elsewhere to the units at sea could this gigantic work
have been expeditiously accomplished. It frequently happened that any
delay due to very severe weather in clearing a field or area meant
complete stoppage or chaotic dislocation of the almost continuous stream
of merchant shipping entering and leaving a big harbour, which, in turn,
disorganised the adjacent harbours to which ships had often to be
diverted. It disturbed the railway facilities for the rapid transport of
the food or raw materials from the coast to the manufacturing centres,
from the sugar on the breakfast-table to the shells for the batteries in
France. One hour's delay in unloading a ship may mean three hours'
additional delay on the railways, the loss of a shift at a munition
works and a day's delay in a great offensive. It is a curious anomaly,
made vividly apparent to those in administrative command during the past
years of stress, that the more perfect the organisation the greater the
delay in the event of a breakdown in the system.

There were various methods of minesweeping, but in all of them the
object was to cut the mooring wire of any mine that came within the area
of the sweep and so cause the mine itself to bob up to the surface,
where it could be seen and destroyed by gun-fire. In