The Chart D shows the respective areas at one period. No very important changes took place in the delimitation of the areas during the war, and the chart may therefore be considered generally representative of the organization. Chart E shows the zones into which the Mediterranean was divided.
[Transcriber's note: Charts D and E are maps of the waters around the United Kingdom, and the waters of the Mediterranean, respectively, with patrol zones marked.]
In December, 1917, the number of vessels of different classes actually appropriated to various areas is given on the next page in Table D for the British Isles and Table E for the Mediterranean.
TABLE D: AUXILIARY PATROLS IN HOME WATERS.
------------------------------------------------------------+
Boom Defence Drifters, etc. |
--------------------------------------------------------+ |
Boom Defence Trawlers. | |
----------------------------------------------------+ | |
Patrol Paddlers. | | |
-------------------------------------------------+ | | |
Paddle or Screw Minesweepers. | | | |
----------------------------------------------+ | | | |
Motor Boats. | | | | |
-------------------------------------------+ | | | | |
Motor Drifters. | | | | | |
----------------------------------------+ | | | | | |
Other Drifters. | | | | | | |
------------------------------------+ | | | | | | |
Net Drifters. | | | | | | | |
--------------------------------+ | | | | | | | |
Motor Launches. | | | | | | | | |
----------------------------+ | | | | | | | | |
Whalers. | | | | | | | | | |
------------------------+ | | | | | | | | | |
Trawlers. | | | | | | | | | | |
--------------------+ | | | | | | | | | | |
Yachts. | | | | | | | | | | | |
----------------+---+---+---+---+---+---+--+--+--+--+---+---+
Area No. | | | | | | | | | | | | |
| | | | | | | | | | | | |
I | 5| 44| 4| 6| 22| 2|11| | 3| | | 6|
II | 6|119| 7| 15| 72|112| 6| | 8| | 60| 83|
IV | 1| 27| | 12| 10| 3| | | | | 15| 10|
V | 1| 20| | 8| 12| 1| 7| | | | | |
VI | 6| 51| 1| 24| 9| 14|14| |13| | 20| 23|
VIII | 1| 51| | 16| 25| | 4| | 9| | | |
IX | 1| 93| 3| 6| 25| 1| 4| | 8| | 7| 25|
[ | 2| 16| | 6| 27| | | 2| | | | |
X -[ | | 53| | 6| | 19| | | | | | |
- | | 30| | 6| 28| | 2| | 7| | | 5|
- | 1| 29| | 33| 42| | | | 9| | 3| 13|
XI | 2| 70| | 31|101| | | |19| | | 2|
| 1| | | | | 30| | | | | | |
XII | 2| 35| | 26| 22| 10| | | 6| | | 10|
| | 18| | 5| 18| | | | | | | |
| | 14| | 2| 25| 2| | | | | | |
| | 6| | | | | | | | | | |
| | | | 4| 37| | | 1| | | | |
XIII | 1| 27| | 19| 15| | | | 5| | | |
XIIIA | | 54| | 21| 19| | | | | | | 1|
XIV | 2| 44| | 14| 41| | | | | | | 2|
| | 6| | 6| 6| | | | 5| | | |
XV | 3| 46| | 8| 59| 2| | | | | 3| |
XVI | 3| 19| | 12| 13| | | | | | | 1|
| | 9| | 6| 16| | 5| | 5| | | |
XVII | 3| 26| | 12| 68| 1| | | 4| | | 1|
| 1| 10| | 6| 31| | | | | | 4| 2|
XVIII | | 31| | | 11| 4| | | | | 4| |
XIX | | 7| | 8| | | | | | | | |
XX | | 8| | 6| 4| | | | | | | 1|
XXI | 1| 15| | 16| 11| | 6| | 7| | 2| 3|
XXII | 1| 10| | 6| 14| | | | | | | |
----------------+---+---+---+---+---+---+--+--+--+--+---+---+
TABLE E: AUXILIARY PATROLS IN THE MEDITERRANEAN ZONES
----------------+---+---+---+---+---+---+--+--+--+--+---+---+
I | 7| 9| | 19| | | | | | | | |
VI | 1| 12| | 42|116| | | | | | | |
VIII | 2| 61| | 21| 25| | | | | | 2| 2|
V | 1| 51| | 18| | | | | | 5| | |
X | 1| 47| | 17| 6| | | | | 5| | |
| 2| | | 12| | | | | | | | |
| 2| 22| | | 4| | | | | | 2| |
| 1| 4| | 11| | | | 7| | | | |
----------------+---+---+---+---+---+---+--+--+--+--+---+---+
It will be seen that the total number of British patrol and minesweeping craft, exclusive of the stationary boom defence vessels, was at this time 3,084. Of this number 473 were in the Mediterranean, 824 were in the English Channel between The Nore and Falmouth, 557 were in Irish waters or on the west coast of England, and the remaining 1,230 were on the east coast of England and the east and west coasts of Scotland and the Orkneys and Shetlands.
The work of these vessels was almost entirely of an anti-submarine or minesweeping nature.
The trawlers were engaged in patrol duty, convoy escort service, and minesweeping. The drifters worked drifting nets fitted with mines as an anti-submarine weapon, and also in the case of the Dover area they laid and kept efficient a barrage of mine nets off the Belgian coast. Some were also fitted with hydrophones and formed hunting flotillas, and some were engaged in minesweeping duties, or in patrolling swept channels. At Fleet bases a small number were required to attend on the ships of the Fleet, and to assist in the work of the base. The whalers, being faster vessels than the trawlers, were mostly engaged on escort duty or on patrol. The motor launches were employed for anti-submarine work, fitted with hydrophones, and worked in company with drifters and torpedo-boat destroyers, or in minesweeping in areas in which their light draught rendered it advantageous and safer to employ them instead of heavier draught vessels to locate minefields, and in the Dover area they were largely used to work smoke screens for operations on the Belgian coast.
As the convoy system became more general, so the work of the small craft in certain areas altered from patrol and escort work to convoy duty. These areas were those on the East Coast and north-west of Scotland through which the Scandinavian and East Coast trade passed, and those in the Channel frequented by the vessels employed in the French coal trade. The majority of these ships were of comparatively slow speed, and trawlers possessed sufficient speed to accompany them, but a few destroyers of the older type formed a part of the escorting force, both for the purpose of protection and also for offensive action against submarines attacking the convoys, the slow speed of trawlers handicapping them greatly in this respect.
The difficulty of dealing with submarines may be gauged by the enormous number of small craft thus employed, but a consideration of the characteristics of a submarine and of the great volume of traffic passing up and down our coasts will assist in a realization of the varied and difficult problems set to the British Navy.
For instance, the total number of vessels passing Lowestoft during the month of April, 1917, was 1,837 British and Allied and 208 neutral, giving a daily average of 62 British and Allied and 7 neutral ships; and as Admiral Sir Reginald Bacon has mentioned in his book, "The Dover Patrol, 1915-17" (page 51), an average of between 80 to 100 merchant vessels passed Dover daily during 1917. A study of these figures gives some idea of the number of targets offered daily to ordinary submarines and minelaying submarines in two of the areas off our coasts. When it is borne in mind that the Germans had similar chances of inflicting heavy losses on our mercantile marine all round the coasts of the United Kingdom, and that it was obviously impossible to tell where an underwater attack would take place, it will be realized that once submarines reached our coasts, nothing short of an immense number of small craft could deal satisfactorily with the situation, and afford any degree of protection to trade. Minelaying by submarines was a particularly difficult problem with which to deal; the enemy frequently changed his methods, and such changes when discovered involved alterations in our own procedure. Thus for some time after the commencement of minelaying by submarines, the whole of the mines of one submarine would be laid in a comparatively small area. It was fairly easy to deal with this method as a dangerous area was proclaimed round the spot where a mine was discovered, and experience soon showed the necessary extent of area to proclaim. Later the submarines laid mines in groups of about six. This necessitated the proclamation of more than one area, and was naturally a more difficult problem. At a further stage the submarines scattered their mines in even smaller numbers, and the task of ensuring a safe channel was still further increased. The most difficult artifice to deal with, however, was the introduction by the Germans of a delay action device in their mines, which caused them to remain at the bottom for varying periods after being laid. The ordinary mine-sweep, the function of which was to catch the mooring rope of the mine and drag the mine clear of the channel, was, of course, ineffective against the mine on the bottom, and there was no guarantee that mines might not be released from the bottom and rise to a depth at which they were dangerous, after the channel had been swept and reported clear. To deal with this danger a chain-sweep to work on the bottom was introduced, but its use presented many difficulties, especially over a rocky bottom.