The continuous development of the mine and the torpedo makes it impossible to establish a close watch with heavy ships on the exits from the Heligoland Bight. To do so for a long period of time would mean a steady and serious wastage of valuable units from the above causes, and, if prolonged, would effectually alter the balance of naval power. On the other hand, torpedo craft, which cannot keep at sea like great vessels, and must every three or four days return to port for rest and replenishment, have no base nearer than Harwich, 240 miles away. The operation of controlling the debouches from the Heligoland Bight by means of flotillas would require twice the number of oversea torpedo craft that we now possess. The watch would have to be maintained in three reliefs: one on duty, one in transit, and one at rest, and therefore only a third of the existing vessels would be available at any given time. Such a force could be overwhelmed by a sudden attack of two or three times their numbers by a well-chosen blow, opportunities for which would frequently recur. Unless, therefore, we were to take by storm some fortified German island which could be held as a base, or were permitted to use Dutch or Danish territory, the closing of the debouches of the Heligoland Bight by a close flotilla cordon is, in the opinion of the Admiralty, impracticable at present. The development of submarines of ocean-going capacity may be expected to modify this situation in our favour. The problem of controlling the alternative debouches from the Baltic by watching over the Skaw or the Belts presents many of the features that have been found so unfavourable in regard to the Heligoland Bight. Nothing effective could be done, or still less maintained, with our present forces without using the territory of Norway or Denmark, or both. It must be borne in mind that the enemy have the option of striking with their whole force on either line. * * * * *