The anti-submarine patrols were composed of five ships each, under the command of the senior officer of the unit--frequently a lieutenant with the responsibility of a captain. Their work lay out on the wastes of sea lying between England and Germany. It was seldom that the whole five vessels of each unit cruised together, the usual method being to scatter over the different "beats" and rendezvous in a given latitude and longitude at a specified time and date. They were usually able to communicate with each other and with the base on important matters by wireless. Their periods at sea varied from ten days to three weeks, with a four days' "stand off" when they came into harbour. But of this time one day at least was spent in coaling and provisioning the ship ready for the next patrol. This ceaseless vigilance on the grey-green seas of England's frontier was seldom interrupted for more than a few days in the year by impossible gales. Anything short of literally mountainous seas did not prevent the trawler patrols from riding out the storm carefully battened down and with just sufficient speed to keep head to sea. The drifters were divided into patrol units, boom defence flotillas and under-water or mine-net units. Their work was thus more varied but equally as arduous and risky, as the loss of 30 per cent. of the entire fleet of over 1000 ships affords undeniable proof. The periods of sea duty were similar to those of the trawlers. The motor launches at each base had some hundred square miles of sea to guard, and hunted in fives. The rough weather these plucky little ships endured in the open sea in mid-winter, the intense cold--for there was no proper heating appliance--and the state of perpetual wetness made their duties among the most arduous in the sea war. Later pages of true narrative will show to the full the work of these gnats of the sea. In addition to all these flotillas there were convoy ships, whaler patrols, "Q" boats and a number of special duty ships. The work of the former was of the most exacting character, and left the crews of these vessels but little time ashore. In the base under review so arduous were the duties of the convoy ships that it became a matter of self-congratulation for patrol and sweeper officers and men that their ships were not so employed, and this by men who sailed submarine and mine infested seas for an average of 270 days in each year! It must not be assumed that when in harbour there were no duties to be performed by either officers or men of sea-going ships. They had, on the contrary, to furnish anchor watches, shore sentries, duty crews for emergency pickets, prisoner guards, working and church parties, to attend drills, rifle practice, gun practice and instructional parades. The officers had similar shore duties to perform, which left them little time to rest from the strain of keeping watch and ward on the death-strewn seas. CHAPTER IX THE CONVOY SYSTEM