a line of defense against rebel raids. If troops can be spared for that purpose, some point south of the Potomac should be fortified strong enough to resist any coup de main, and garrisoned with a force which can operate against a rebel advance either down the Shenandoah or the Loudoun Valley. Winchester and Strasburg are both reported as indefensible except by very extensive lines and large garrisons. I do not know that Front Royal has been examined by engineer officers in regard to its defensive character. I am of the opinion, however, that the proper position for such occupation can be found at Manassas Gap, or in its vicinity, so that the garrison my operate on either side of the Blue Ridge, as occasion may require. The place so selected and fortified should have several months' supplies and be capable of making a strong and long resistance to an attacking force. It can be communicated with by the Manassas railroad, which must be protected by entrenched garrisons at Thoroughfare Gap and Manassas Junction, and by cavalry pickets on Broad Run and across to Chester Gap and Strasburg or Woodstock. In order to keep up communication on this line to Manassas Gap and the Shenandoah Valley, it will be necessary to send South all rebel inhabitants between that line and Potomac, and also to completely clean out Mosby's gang of robbers who have so long infested that district of country, and I respectfully sagest that Sheridan's cavalry should be required to accomplish this object before it is sent elsewhere. The two small regiments under General Augur have been so often cut up by Mosby's band that they are cowed and useless for that purpose. If these dispositions are approved and carried out, it will not be necessary to keep so large a force at Harper's Ferry and guarding the canal and Baltimore and Ohio Railroad. As soon as we can open the road to Piedmont, I will send Colonels Alexander and Thom, of the engineers, to examine the localities above mentioned with reference to fortifications,a nd to confer with General Sheridan. I will also send General Sheridan a copy of this letter. I have no doubt that General Crook might be able to select some points in the great North Mountain or Alleghany Ridge by which a small force could prevent rebel cavalry raids into West Virginia, and thus avoid the necessity of keeping up so many posts there.

Very respectfully, your obedient servant,

H. W. HALLECK,

Major-General and Chief of Staff.

CITY POINT, VA., October 4, 1864-2 p. m.

(Received 3.30 p. m.)

Major-General HALLECK,

Washington, D. C.:

In moving Sheridan's force here, move one division of cavalry as fast as possible. Send all the cavalry horses that can possibly be raised in the meantime. There is danger of the enemy returning a portion of their cavalry here and annoying us greatly with raids on our rear and along the river. Is it not possible to get all the new troops now in the depots to the front at once. I hear of thousands of men all over the North.

U. S. GRANT,

Lieutenant-General.

18 R R-VOL XLIII, PT II