WASHINGTON CITY, July 6, 1863.

To the President of the following Railroads:*

I am informed by the Quartermaster-General that, in order to reap the fruits of victory, a large number of fresh horses are most urgently required. They are needed to remount the cavalry and restore the batteries to a condition of efficiency. Extraordinary efforts should be made by the officers of all railroads over which horses are transported to push them forward without delay, day and night. Please give this subject prompt personal attention. In no other way can more efficient service be rendered at this time to the country. The enemy must not escape if in our power to prevent it.

H. HAUPT,

Brigadier General, Chief of Const'n and Trans., U. S. Military R. R.

HEADQUARTERS ARMY OF THE POTOMAC, July 6, 1863. (Received 4 p. m.)

General MEIGS,
Quartermaster-General:

It will be safe to send horses to Frederick. Those sent will arrive in good time. General Couch will send 500 to this place, and we are procuring all that the country will afford. I have put Captain Rankin on temporary duty in town, to see to surplus property turned in, draw and issue supplies.

We will not move toward Frederick until the enemy shows his intentions. It is quite clear that he is in retreat, demoralized, and embarrassed with muddy roads. Our forces are hemming him in. We hope at least to get back the transportation heretofore lost. It is necessary to be cautious.

RUFUS INGALLS,

Brigadier-General, Chief Quartermaster.

QUARTERMASTER-GENERAL'S OFFICE, Washington, D. C., July 6, 1863-12. 45 p. m .

Brigadier General R. INGALLS,

Chief Quartermaster, Hdqrs. Army of the Potomac:

Captains Hiram Smith and H. B. Blood are ordered to Gettysburg, to collect all property left by both armies in that vicinity.

Sixteen hundred horses and over 2, 000 cavalry, just mounted or remounted, have left this city for Frederick, already. I have advice of several trains of cars, from 100 to 275 horses in each, which, since the railroads have been opened, are on their way to the Army of the Potomac. By telegraph to various points, all horses en route are directed upon Frederick.

-------------------------------------------------------------------

---------------

*Boston and Worcester, Boston, Mass. ; New Haven, Hartford and Springfield, Hartford, Conn. ; Camden and Amboy, New York, Philadelphia, Wilmington and Baltimore, Philadelphia, Pa. ; Cleveland and Toledo, Cleveland, Ohio; Pittsburgh, Columbus and Cincinnati, Steubenville, Ohio; Pennsylvania Central, Philadelphia; Indiana Central, Dayton, Ohio; Cleveland and Pittsburgh, Cleveland, Ohio; New Jersey Railroad Transportation Company, New York; New York and New Haven, New York City; Michigan Southern, Toledo, Ohio.

---------------