HEADQUARTERS POTOMAC DEPARTMENT,
Culpeper Court-House, Va., May 14, 1861.

Colonel R. S. GARNETT, Adjutant-General:

SIR: I report, for the information of the General-in-Chief, that I returned to this place on Sunday morning, the 12th instant, from Manassas Junction, where I had gone to examine the position and the country around, and to make arrangements for gathering a force there for the defense of the place. My observation of the country were mainly directed towards the Potomac, on the right flank, and I find the head of tide, at Occoquan, approached within eighteen miles of Manassas. Mr. John Grant, my acting engineer and topographical draughts man, was sent forward with a guide, to examine the roads towards Occoquan, while I myself rode over the most direct road, to point where it crosses the Occoquan River, seven or eight miles to the right of Manassas Junction. Mr. Grant subsequently pursued this latter road to the village or landing of Occoquan, the head of tide, and I can report that the country upon these routes, covering the right flank of the position at Manassas Junction, is quite favorable for defensive operations, the same being broken or undulating, covered with dense forests of second-growth pines or of original oak, except here, and small fields or farms, the roads very narrow (mere ditches), and everywhere such as to render artillery and cavalry of our enemy on the march of little use to him, while the cover of forests, hills, and ravines make a fortress for brave men and riflemen in which to carry on the destructive guerrilla warfare upon any marching columns form that side. Nevertheless the proximity of the Potomac River, on that side, from Manassas Junction to Alexandria, will ever require extreme vigilance and precaution to cover the right of that line from flank attack at other points, where the ways may be more open and inviting.

The force that I have been enabled to assemble thus far at Manassas Junction consists of a detachment of artillery, under Captain D. Kemper, with two 6-pounders; Captain W. H. Payne's company, numbering 76 men; Captain J. S. Green's company, numbering 57 men; Captain Hamilton's company, numbering about 60, and two Irish companies, numbering, respectively, 54 and 58, and Colonel Garland's force, arrived Sunday, consisting of 490 men. Altogether, about 830 men. Also Captain Marr's company, 88 Warrenton Riflemen. Total, 918. The Powhatan Troop, under Captain Lay, has been order back here, and will arrive to-day.

Should Colonel Terrett make Manassas his headquarters, he will doubtless go on to strengthen it with forces to be gathered within the large and populous district assigned to his immediate command. I have advised Colonel Terrett, through a letter yesterday, addressed to him, not to leave Alexandria himself until he shall be well satisfied that his next in command there will be a man of cool, firm, and otherwise able character, to hold that important outpost so long as it be possible for brave men to hold it.

The General-in-Chief may be assured that I will make all practicable efforts to bring about the speedy assembling, mustering into service, organizing, drilling, and disciplining of the volunteers on my whole line, and to draw from this source as rapidly as possible, to strengthen the main position of this line-a line which even now remains almost wholly open to the enemy, should he decide to march with any force upon it. Indeed, it would seem highly expedient, in view of the now openly acknowledged and accepted state of war on the part of the