The location of the first minefield was decided upon; then further details were settled with Vice Admiral Brock and Rear Admiral Clinton-Baker, for the first mining excursion, which was to be done by the American and British squadrons at the same time. Preparatory notice was to be given by the Commander Mine Force to the Admiral of the Grand Fleet at least four days before the time the mine squadron was expected to be loaded and ready for an excursion. Upon a second, definite notice, not less than 48 hours in advance, when it was certain that the squadron would be ready, a combined operation order would be issued by the Admiral, naming all the forces concerned and containing the instructions and intelligence necessary for all. After lunching on board with Admiral Beatty, Rear Admiral Strauss and I took our leave. We had a look at Holyrood Palace and a walk through Canongate Street that afternoon, returning to Inverness next day. Not enough material had yet been accumulated to assemble mines to fill all seven minelayers present, but 3400 would be ready in a few days, sufficient to lay a field 47 miles long, consisting of one row of mines at each of the three levels prescribed. A mine embarking schedule was made out accordingly, to include _San Francisco_, _Baltimore_, _Roanoke_, _Canandaigua_, _Canonicus_, and _Housatonic_, for a start on June 7. CHAPTER TWO THE NEED AND THE MEANS A barrier of high explosive across the North Sea—10,000 tons of TNT, 150 shiploads of it, spread over an area 230 miles long by 25 miles wide and reaching from near the surface to 240 feet below—70,000 anchored mines each containing 300 pounds of explosive, sensitive to a touch, barring the passage of German submarines between the Orkneys and Norway—this was the final five months’ contribution of the American and British mining forces towards bringing the war to a close. To stop the enemy submarines near their bases, before they could scatter on the trade routes, would obviously defeat their campaign more surely than merely hunting them at large. That was the purpose of the Northern Mine Barrage, which, with the barrage at Dover, made it not impossible but extremely hazardous to enter or leave the North Sea. That many a submarine came to grief in attempting these barriers is now a certainty, and the establishment of the Northern Barrage, which many had thought impossible, insured the early finish of the submarine campaign.