Codes were issued by the Admiralty for use at sea. Their early cryptogram was easily decoded by friend and enemy alike. Knowing that certain words would assuredly be embodied in the text of a message (words such as, _from_--_latitude_--_report_--_submarine_--_master_), it was not difficult to decipher a code of alphabetical sequence. There were famous stories of traitors and spies, but our authoritative simplicity was responsible for the occasional leakage of information. At this date, 1915-16, wireless position-detectors came into use by the enemy. A spark-group, repeated after an interval, could give a fair approximation of distance and course and speed. More than ever it was necessary to maintain silence when at sea. Withal, the air was still in strong voice. At regular periods the great longshore radios threw out war warnings to guide us in a choice of routes and warn us away from mined areas. Patrols and war craft kept up an incessant, linking report. Distress signals hissed into the atmosphere in urgent sibilance, then faltered and died away. On occasion, the high note of a _Telefunken_ set invited a revealing confidence that would lead us, 'chicky-chicky,' to the block. We were well served by Marconi. Extension of the power of enemy submarines brought new practice to our seafaring. We had made the most of a passage by the land, steering so close that the workers in the fields paused in their toil and waved us on; but the new under-water craft crept in as close, and mined the fairways. We were ordered to open sea again, to steer the shortest course by which we could reach a depth of water that could not be mined. Zigzag progress now assumed the importance that was ever its right. It had been but cursorily maintained. The 'shortest distance between two points' had, for so long, been our rule that many masters were unwilling to steer in tangents. On passage in the more open sea, they were soon converted to a belief in the efficacy of a crazy course. Statistics of our losses proved the virtue of the tangent: of a group of six vessels sunk in a certain area only one--a very slow vessel--was torpedoed while maintaining a zigzag. Extracts from the diary of a captured submarine commander were circulated among us, giving ground for our confidence, in the frequent admissions of failure--"owing to a sudden and unexpected alteration of course."