The plan of laying a mine barrage across the North Sea, from the Scottish coast to the Norwegian shore waters, originated with the Ordnance Bureau of the American Navy. For some time the British Admiralty insisted that it was not practicable, but after much discussion they finally consented and the details of the operation of the scheme were worked out together. A new type of mine was demanded, because of the depth of the water, and this and a new firing device had already been developed by the Ordnance Bureau of the Navy. The number of mines required to lay a barrage 245 miles long and 20 miles wide was so enormous and the need to have them ready at the earliest possible moment so urgent that it was impossible to provide them by the usual methods of manufacture. Therefore the mine was divided into its many component parts and these were separately produced in as many as four hundred industrial factories. The parts were partially brought together in sub-assemblies in this country, and were thus shipped to Europe, where the complete assembling was done just prior to issue to the mine planters. There were manufactured 100,000 of these mines, of which about 85,000 were shipped abroad, some of them being used in similar mine barrages elsewhere. For this purpose a fleet of over fifty merchant ships was taken over by the navy and fitted out for the carrying of all this mine material overseas. Out of the entire fleet only one was lost by enemy action. Mine bases were established on the coast of Scotland, many mine layers and auxiliary vessels were fitted out and the work was carried on at a high rate of speed, sometimes as many as a thousand mines a day being laid. The American Navy furnished all the mines and laid 80 per cent of them for this huge barrage, of a greater length and in deeper water than had ever before been thought possible. The barrage was fatal to at least ten submarines within a short time after it was finished, and had the war continued would have reduced the submarine danger to little consequence. Immense quantities of oil were needed on the east coast of Scotland for the British and American ships of the Grand Fleet and other purposes and the practice had been to send it on its journey from the United States in tankers around the north coast of Scotland. But enemy submarines took a heavy toll of the precious liquid and the Navy Department suggested the laying of a pipe line across Scotland. The work of laying the line was mainly done by the American Navy, which furnished the pipe for the work. The line could deliver 100 tons per hour and was the longest in Europe. The entire work was completed in six months and was finished on the day when firing ceased.