Altogether there were 13 regular excursions and two special ones by the American squadron, and 11 by the British squadron. In all, 70,117 mines were planted, of which 56,571, or four-fifths, were American. In its 230 miles length, the barrage varied in width from 15 to 35 miles, so that a submarine could not attempt a crossing without being in danger for from one to three hours, or twice as long, if running submerged. The obstruction extended to a depth of 240 feet, except over the eastern section of 50 miles length, where the deepest mines were submerged 125 feet. In small fields, of a few score or hundreds of mines, laid piecemeal by fixed marks, the mines in adjacent lines are usually “staggered,” so as to halve and block the opposite intervals, but in an open-sea minefield of immense area, far beyond sight of any marks and laid at 12 knots speed or faster, no such nicety is possible or necessary. The great Northern Barrage opposed from 6 to 10 lines of mines to a submarine on the surface and three to four lines more at whatever depth the submarine might think he could safely pass. Absolute impassability never was attained nor expected. At the thickest part a submarine had one chance in ten of getting through. The explosion of defective mines had left some thin spots—but who could tell where? Such a minefield is not so much like a Chinese wall as it is like a stretch of rough, treacherous country, whose crossing would always be a desperate venture. Submarines are known to have crossed the barrier, but they all feared it, and as early as 8 July, 1918, some experienced its deadly effect. From the very circumstances of the barrier’s great extent and the absence of observers, the full toll, in damage as well as destruction, may never be known. The official statistics of lost German submarines, compiled March 1, 1919, credit the Northern Barrage with the destruction of four submarines certainly, two more probably, and possibly still two more. An equal number were severely damaged, though not destroyed, and it is considered probable by the British Admiralty that the loss of five other submarines, the cause of which cannot be definitely proven, is accounted for by the Northern Barrage. Thus by reliable records, the toll was 17. Indications during the sweeping up of the barrage tend to confirm this. Besides these, to the squadron’s credit, should be added the two submarines reported lost in the North Irish Channel, in the field which consisted of British mines laid by our _Baltimore_. The summary of Activities of U.S. Naval Forces in European Waters, issued by Admiral Sims, says further: There is no doubt that this barrage had a considerable moral effect on the German naval crews, for it is known that several submarines hesitated some time before crossing. Also, reports from German sources are that the barrage caused no small amount of panic in some of the submarine flotillas.