OR, Series 1, Vol. 30, Part 4, Page 503

War Department, Engineer Bureau
Richmond, August 8, 1863
General J. E. Johnston
Commanding Western Department, Enterprise, Miss.
  To keep in repair the main lines of railroad essential to the support and transportation of our armies, iron rails and rolling stock must be obtained from every available source. Will it be possible for the engineers serving in your department to build a temporary bridge over the Pearl River at Jackson, and make such other repairs as will enable them to save the engines, cars, and a part of the rails from the Mississippi Central Road?
  Major Meriwether, Captain Porter, and other engineers with your command, have had much experience as civil engineers, and can direct all the operations, if by your authority the requisite labor and material can be obtained. It is hoped slave labor can be obtained; if not, the work might be accomplished, possibly, by details from the troops.
  Will you please to inform this bureau whether the branch railroad to Marion, Ala., known as the Cahaba, Marion & Greensborough road, is in any way important to the operations of the army under your command. If not, the want of railroad bars for repairing the main lines is so great, it is proposed to move the iron from the branch.
I am, general, very respectfully, your obedient servant,
J. F. Gilmer
Colonel of Engineers and Chief of Bureau