stop the sailing of the outward convoys.  Again, outward convoys were often delayed by bad weather, resulting in the homeward convoy not being met before entering the submarine zone.  As the winter drew near this was a source of constant anxiety, since so many of the vessels outward bound were in ballast (empty), and their speed was consequently quickly reduced in bad weather.  The ships under these conditions became in some cases almost unmanageable in a convoy, and the responsibilities of the escorts were much intensified.

In September, 1917, the following was the position in respect to outward bound convoys: 

Port of Assembly.  Frequency of Sailing.  Destination.

Lamlash                   Every 4 days.               Atlantic ports. 
Milford Haven             Every 4 days.               Gibraltar. 
Queenstown                Every 4 days.               Atlantic ports. 
Falmouth                  Every 8 days.               Gibraltar. 
Plymouth                  Every 4 days.               Atlantic ports.

About 150 vessels sailed every eight days in convoys varying in strength from 12 to 30 ships.

There was still a good deal of Atlantic trade that was not sailing under convoy.  This comprised trade between Gibraltar and North and South America, between the Cape, South America and Dakar, and the coastal trade between North and South America.  It was estimated that an additional twenty-five to thirty ocean escorts and eleven destroyers would be needed to include the above trade in convoy.

The Mediterranean trade is dealt with later.

The question of speed was naturally one of great importance in the convoy system.  As has been stated earlier, the speed of a convoy like that of a squadron or fleet is necessarily that of the slowest ship, and in order to prevent delay to shipping, which was equivalent to serious loss of its carrying power, it was very necessary that convoys should be composed of ships of approximately the same speed.  In order to achieve this careful organization was needed, and the matter was not made easier by the uncertainty that frequently prevailed as to the actual sea speed of particular merchant ships.  Some masters, no doubt from legitimate pride in their vessels, credited them with speeds in excess of those actually attained.  Frequently coal of poor quality or the fact that a ship had a dirty bottom reduced her speed to a very appreciable extent, and convoy commodores had occasionally to direct ships under such conditions to drop out of the convoy altogether and make their passage alone.  Obviously this action was not taken lightly owing to the risk involved.  Decision as to the sea speed of convoys was taken by the convoy officer at the collecting port, and he based this on the result of an examination of the records in the different ships.  As a rule convoys were classed as “slow” and “fast.”  Slow convoys comprised vessels of a speed between 8 and 12-1/2 knots.  Fast convoys included ships with a speed between 12-1/2 and 16 knots.  Ships of higher speed than 16 knots did not as a rule sail in convoys, but trusted to their speed and dark hours for protection in the submarine area.  The Gibraltar convoy (an exception to the general rule) contained ships of only 7 knots speed.