cars a day, with exceptional days on which the delivery ran higher; but a steady average of a hundred and fifty (the needed quantity) had not been reached, and every day's advance into Georgia would increase the length of the line. [Footnote: Official Records, vol. xxxii. pt. iii. pp. 466, 490.] In a characteristic letter to General Thomas, Sherman explained the necessity of having the railway management directed from his own headquarters instead of those of the Army of the Cumberland, and in one to Mr. Lincoln he tersely repelled the idea that he was unduly hard on the inhabitants of the country and their business. [Footnote: _Id_., p. 489; and vol. xxxviii. pt. iv. pp. 25, 33.] General Meigs, the quartermaster-general, who knew the country by personal inspection, fully agreed with Sherman and wrote him on April 20th, advising him to "resist the pressure of civilians and private donations and supplies; march your troops, and devote the cars solely to transportation of military necessities.... Many civilians," he added, "can give charitable, patriotic, benevolent, and religious reasons to be allowed to go to the front; the reasons are so good that nothing but an absolute and unchangeable prohibition of all such travel will do any good." [Footnote: _Id_., vol. xxxii. pt. iii. p. 434.] The business management of the military railways was a matter of greatest importance, but it must be supplemented by an adequate system of defence. To cut the long line and interrupt the communications of the army would, of course, be the constant effort of the enemy. Every wooden bridge across a stream was a most vulnerable point. A burnt bridge meant a delay of trains till it could be rebuilt, and Sherman's estimate that he must receive at the front a hundred and fifty car-loads daily, shows how soon trouble would be caused if the steady roll of car-wheels should cease. For the freight cars of that day, ten tons made a load, and with the light locomotives and iron rails then in use, twenty or thirty cars made a full train. A system of blockhouses for the protection of the bridges had been gradually developed by the engineers of the Army of the Cumberland on suggestions made by General Halleck and others, and was under the charge of Colonel W. E. Merrill, who enlarged and improved it. This able officer was retained at the head of the defensive system, and his success in it was noteworthy. [Footnote: Colonel Merrill has given a valuable memoir on the construction and use of the blockhouses, in "Ohio Loyal Legion Papers," vol. iii. p. 389. After the war, he was for many years United States Engineer in charge of Ohio River improvements.]