It was regarded as being of so great importance to obtain the earliest possible warning of Hun activities in the North Sea that an order was issued by the Admiralty to the effect that a submarine on lookout patrol had for her primary duty to come to the surface and send home, by wireless, information as to _outward_-bound enemy surface craft; while her secondary duty was to attack. In the case of _homeward_-bound enemy surface craft, the primary duty was to attack. If there should be any doubt as to the destination of an enemy surface craft, it was the duty of the submarine first to report by wireless and then to attack. I have already shown how, during the critical eight days that saw our First Expeditionary Force cross the Channel to France, the Harwich submarines kept a sleepless watch on the German coast, to attack the enemy ships should they come out to interfere with the transport of our troops. I have also explained that these submarines had a good deal to do with the preparation for the action in Heligoland Bight. It was the E23, too, of this flotilla that, while patrolling, sighted the German High Sea Fleet on August 19, 1916. She first wirelessed home the news that the Germans had come out, and then delivered a bold attack. She torpedoed the battleship _Westphalen_ on the port side. The result of the explosion gave the battleship a big list, but for a while she still went on with the battle fleet. As the list increased, she at last left the line and turned for home, escorted by destroyers. Thereupon the E23 set out to intercept her, passed through the screen of enemy destroyers that were zigzagging round the _Westphalen_, and torpedoed her on the starboard side. The battleship contrived to get away, but in so damaged a condition that she must have been out of the war for a considerable time. The strategical position occupied by the Harwich Flotilla also imposed upon it another duty of great responsibility. The submarines had to be ever ready to go south at a moment's notice to cover the eastern approach to the English Channel against the enemy capital ships, should these attempt to break through. Had the Germans made the attempt in earnest, there is no doubt that they would have had to pay a very heavy toll. Admiral Sir David Beatty put it well when, in a speech delivered in Edinburgh, he spoke of our "submarine sentinels who carried out the same services as the storm-tossed frigates of Cornwallis off Brest." The only British submarines that were adapted for the laying of mines were those of the Harwich Flotilla. Consequently, for a considerable time plenty of arduous, perilous work among the minefields fell to their lot.