The intention being to lay the barrage as soon as possible, and counting five days as the least time between minelaying operations—coaling, embarking mines, out, laying, and back—the expected manufacturing output of 1000 mines a day demanded a minelaying squadron with capacity of 5000 mines at one time. Towards this, our _San Francisco_ and _Baltimore_ carried together only 350 mines. The eight new vessels would add 5350, thus providing a good margin, either for the loss of a ship or for speeding up. No time was to be lost. The demand for ships, shipyard work, and ship equipment for other purposes was increasing every day. Within 10 days the Eastern Steamship Corporation’s fast passenger liners _Massachusetts_ and _Bunker Hill_, running daily between New York and Boston, were purchased outright, becoming the _Shawmut_ and _Aroostook_. Within a month the Southern Pacific freight steamers _El Rio_, _El Dia_, _El Cid_, and _El Siglo_ were taken over, becoming _Roanoke_, _Housatonic_, _Canonicus_, and _Canandaigua_, respectively. Carrying 860 mines each they soon became known as the Big Four. The Old Dominion steamers _Hamilton_ and _Jefferson_, familiar to passengers between New York and Norfolk, followed by December 6, 1917. [Illustration: THE BOSTON-NEW YORK PASSENGER LINER “MASSACHUSETTS.” Before conversion into a minelayer.] The task of making four freight ships habitable for crews of 400 men, at the same time carrying twice as many mines as any other vessel of their size, is not done by a wave of the hand, and as for the four passenger steamers taken, they were gutted like fish—saloons and cabins ripped out—before their conversion could begin. Although plans had to be based upon what could be done within a reasonable time, with material and labor scarce, all features had to conform to the requirements of the mining installations. These were almost entirely new on the scale contemplated, either in our own or any other service. There was little data available of similar installations, except some British mining memoranda and a few belated blueprints. Lieutenant DeSalis, R.N., kindly placed his experience at our disposal, which was a help, but attempts abroad had not made a success of mine elevators—which would form a cardinal feature of our installation—nor had others gone in for mine-carrying capacity to the extent we contemplated—which was the maximum number consistent with not squeezing the crew intolerably. Hence, little of their information proved applicable to our case. Experience in our own minelayers, however, _San Francisco_, _Baltimore_, and _Dubuque_, during the past three years, enabled many details to be decided with a confidence that subsequent results confirmed. [Illustration: THE 20-KNOT MINELAYER “SHAWMUT.” Formerly the coastwise passenger liner _Massachusetts_.]