Nazaire; it was to be their main mission to destroy the "Big Bertha" which was raining shells on Paris, and to attack specific points, especially railroad communications and the bridges across the Rhine. The initiative in the design of these mobile railway batteries was taken by the Bureau of Ordnance of the Navy Department, under Rear-Admiral Ralph Earle, and the details of the design were worked out by the officers of that bureau and Admiral Plunkett. The actual construction of the great gun mounts on the cars from which the guns were to be fired, and of the specially designed cars of the supply trains for each gun, was an engineering feat which reflects great credit upon the Baldwin Locomotive Works and particularly upon its president, Mr. Samuel M. Vauclain, who undertook the task with the greatest enthusiasm. The reason why our naval guns represented a greater achievement than anything of a similar nature accomplished by the Germans was that they were mobile. Careful observations taken of the bombardment of Dunkirk revealed the fact that the gun with which it was being done was steadily losing range. This indicated that the weapon was not a movable one, but that it was firmly implanted in a fixed position. The seventy-five mile gun which was bombarding Paris was similarly emplaced. The answering weapon which our ordnance department now proposed to build was to have the ability to travel from place to place--to go to any position to which the railroad system of France could take it. To do this it would be necessary to build a mounting on a railroad car and to supply cars which could carry the crews, their sleeping quarters, their food and ammunition; to construct, indeed, a whole train for each separate gun. This equipment must be built in the United States, shipped over three thousand miles of ocean, landed at a French port, assembled there, and started on French railroads to the several destinations at the front. The Baldwin Locomotive Works accepted the contract for constructing these mountings and attendant cars; it began work February 13, 1918; two months afterward the first mount had been finished and the gun was being proved at Sandy Hook, New Jersey; and by July all five guns had arrived at St. Nazaire and were being prepared to be sent forward to the scene of hostilities. The rapidity with which this work was completed furnished an illustration of American manufacturing genius at its best. Meanwhile, Admiral Plunkett had collected and trained his crews; it speaks well for the _moral_ of the Navy that, when news of this great operation was first noised about, more than 20,000 officers and men volunteered for the service.