defeated the rebel army in a severe engagement at Gettysburg. From Frederick our army moved toward Hagerstown and Williamsport, and lines were at once extended from the first-named place to the headquarters of General Meade and to the several corps headquarters. These lines were worked continually until after the rebel army had evacuared Williamsport, when the main force of our army moved to Pleasant Valley, Md., the headquarters of General Meade being established at Knoxville. Lines were then built to the army, connecting with our line to Harper's Ferry.
July 19 and 20, our army crossed the Potomac near Berlin, Md., and immediately moved to Gainesville, Va., where telegraph communication with Washington was renewed via Manassas Gap Railroad. within a few days the army marched to the line of the Orange and Alexandria Railroad. From this time until May, 1864, when the army bean its spring campaign, two wires were kept in constant working order from Washington to the army, one being used exclusively for military, the other for railroad business. In addition to these lines others were built from General Meade's headquarters to all of the corps and some of the division headquarters. These lines were of very great value to the army, keeping all its parts in quick communication with each other and with Washington. In March, 1864, the Secretary of War ordered the constructions of a telegraph line from Washington, D. C., via port Tobacco, to Point Lookout, Md., that being the new depot for rebel prisoners of war. This line was commenced March 14 and finished April 3, offices being opened at Point Lookout, at Saint Mary's, the headquarters of the Potomac flotilla, at Port Tobacco, and afterward at Leonardtown, Md. The use of this line has been of immense advantage to the Government. From June, 1862, a field telegraph had been worked in the Army of the Potomac under the supervision of the Signal Corps, the wire used being if steel (six strands), covered with rubber, and the instrument the Beardslee magneto-electirc machine. This instrument was found to be inefficient for speedy communication and failed to accomplish the result desired. In march, 1864, by an order of the secretary of War, these field telegraph lines and instruments were turned over to me to be worked. I gave them a through trial. The instruments proved to be of very little practical use, and were sent to the rear, by order of Major-General Meade, previous to the movement of the army.
In comtemplation of the spring campaign of the Army of the Potomac, a complete field telegraph construction and working party was organized under charge of D. Doren, superintendent of construction, and A. H. Caldwell, chief operator. An arrangement for the speedy running out of telegraph wire was made as follows: Pack-saddles were fitted for reels, each containing one mile of wire, and were placed on pack-mules. By making fast the end of the wire and starting the mules off the wire was unwound and run out with great rapidity. This arrangement has enabled us to construct field lines with great promptness, many times having them up and working before the troops themselves had changed position. To furnish current for the army lines, I fitted up a portable battery, consisting of sixteen sections of six cells each. The cells are of cooper, about four inches in diameter and nine in depth, and contain a solution of blue vitriol and water. In this colution in placed a leather cup one-half the diameter of the cup one-half the diameter of the copper, containing a zinc plate and water. Each cell is insulated by a casing of thin sheet rubber, and fitted on the tap is a bone rubber cap, thus making the cells water-tight. Each section is inlosed in a strong box,