The reconstruction of this particular line was more especially needed in connection with General Sherman's campaign in Georgia and the Carolinas--a campaign which afforded the greatest and most direct evidence up to that time alike of the possibilities of rail-power in warfare, of the risks by which its use was attended, and of the success with which those risks could be overcome by means of efficient organisation. In that struggle for Atlanta which preceded his still more famous march to the sea, Sherman had with him a force of 100,000 men, together with 23,000 animals. His base of supplies, when he approached Atlanta, was 360 miles distant, and the continuance of his communications with that base, not only for the procuring of food, clothing, fodder, ammunition and every other requisite, but for the transport to the rear of sick and wounded, refugees, freedmen and prisoners, depended on what he afterwards described as "a poorly-constructed single-track railroad" passing for 120 miles of its length through the country of an extremely active enemy. Yet Sherman is said to have made his advance in perfect confidence that, although subject to interruptions, the railway in his rear would be "all right"; and this confidence was fully warranted by the results accomplished. Early in September, 1864, the Confederate General, Wheeler, destroyed seven miles of road between Nashville and Murfreesboro', on the Nashville and Chattanooga Railway, and in the following December Hood destroyed eight miles of track and 530 ft. of bridges between the same stations; yet the arrangements of the Federal Construction Corps allowed of the repairs being carried out with such promptness that in each instance the trains were running again in a few days. The Confederate attacks on the Western and Atlantic Railway, running from Chattanooga at Atlanta, a distance of 136 miles, were more continuous and more severe than on any other line of railway during the war; but, thanks again to the speed with which the repair and reconstruction work was done, the delays occasioned were, as a rule, of only a few hours, or, at the most, a few days' duration. One especially remarkable feat accomplished on this line was the rebuilding, in four and a half days, of the Chattahochee bridge, near Atlanta--a structure 780 ft. long, and 92 ft. high. Hood, the Confederate General, thought still further to check Sherman's communications by passing round the Federal army and falling upon the railway in its rear. He succeeded in tearing up two lengths of track, one of ten miles, and another of twenty-five miles, in extent, and destroying 250 ft. of bridges; but once more the work of restoration was speedily carried out, McCallum saying in reference to it:--