These details may convey some idea of all that was involved in the utilisation of rail-power in the American Civil War under such development of railway construction as had then been brought about. Great, however, as was the outlay, the forethought, the energy, the patience and the watchfulness spoken of by McCallum, the results were no less valuable from the point of view of the Federals, who could hardly have hoped to achieve the aim they set before themselves--that of saving the Union--but for the material advantages they derived from the use of the railways for the purposes of the campaign. Some of the achievements accomplished in the movement of troops from one part of the theatre of war to another would have been creditable even in the most favourable of circumstances; but they were especially so in view alike of the physical conditions of many of the lines, the inadequate supply of rolling stock, and the risks and difficulties to be met or overcome. One of these achievements, carried out in September, 1863, is thus narrated in an article on "Recollections of Secretary Stanton," published in the _Century Magazine_ for March, 1887:-- The defeat of Rosecrans, at Chickamauga, was believed at Washington to imperil East Tennessee, and the Secretary [of War] was urged to send a strong reinforcement there from the Army of the Potomac. General Halleck (General-in-Chief of the Army of the United States) contended that it was impossible to get an effective reinforcement there in time; and the President, after hearing both sides, accepted the judgment of Halleck. Mr. Stanton put off the decision till evening, when he and Halleck were to be ready with details to support their conclusions. The Secretary then sent for Colonel McCallum, who was neither a lawyer nor a strategist, but a master of railway science. He showed McCallum how many officers, men, horses, and pieces of artillery, and how much baggage, it was proposed to move from the Rapidan to the Tennessee, and asked him to name the shortest time he would undertake to do it in if his life depended on it. McCallum made some rapid calculations, jotted down some projects connected with the move, and named a time within that which Halleck had admitted would be soon enough if it were only possible; this time being conditioned on his being able to control everything that he could reach. The Secretary was delighted, told him that he would make him a Brigadier-General the day that the last train was safely unloaded; put him on his mettle by telling him of Halleck's assertion that the thing was beyond human power; told him to go and work out final calculations and projects and to begin preliminary measures, using his name and authority everywhere; and finally instructed him what to do and say when he should send for him by and by to come over to the department. When the conference was