The known number of enemy submarines and their rate of construction, allowing liberal factors for errors of information, renders it inevitable that the main submarine effort must continue to be concentrated in the above critical area. 12. Even in this critical area, it is manifest that the field is relatively large for the maximum number of submarines which the enemy can maintain in it. For example, with the present Admiralty policy (explained below) they are forced to cover all the possible trade routes of approach between the north of Scotland and Ushant. 13. From consideration of the above and all other essential information available, it is apparent that the enemy could not disperse his main submarine campaign into other quarters of the Globe without diminishing results in this and all areas to a degree which would mean failure to accomplish the Mission of the submarine campaign, which can be nothing else than a final decision of the war. 14. Considerable criticism has been, and still is, concentrated upon the Admiralty for not taking more effective steps and for failing to produce more substantial and visible results. One of the principal demands is for convoys of merchant shipping, and more definite and real protection within the war zone. The answer, which manifestly is not publicly known, is simply that the necessary vessels are not available, and further that those which are available are suffering from the effects of three years of arduous service. 15. It is insistently asked (was asked by myself) why shipping is not directed to and concentrated at various rendezvous and from these convoyed through the dangerous areas. The answer is the same--the area is too large; the necessary vessels are not available. 16. However, I am now consulting with the Director of Shipping as to the practicability and advisability of attempting some approach to such a plan in case the United States is able to put in operation sufficient tonnage to warrant it. 17. After trying various methods of controlling shipping, the Admiralty now believes the best policy to be one of dispersion. They use about six relatively large avenues or arcs of approach to the United Kingdom and Channel, changing their limits or area periodically if necessity demands. Generally speaking, one is to the north of Scotland, another to the north of Ireland, and three or four others covering the Irish Sea and Channel. Individual ships coming into any of these areas of approach are instructed, generally before sailing, to cross the twentieth meridian at certain and different latitudes and thence steer certain courses to port. At times in the past they have found one of these avenues of approach free of submarines under such conditions as to lead them to concentrate shipping therein, but invariably the enemy has become aware of the course pursued.