It was noon when we arrived at Fairfax Court-House — a poor village of some 30 or 40 straggling wooden and brick houses, deriving its name from the building in which the Circuit Court of the county is held, I believe, and looking the reverse of flourishing — and one may remark, obiter, that the state of this part of Virginia cannot be very prosperous, inasmuch as there was not a village along the road up to this point, and no shops or depots, only one mill, one blacksmith and wheelwright. The village was held by a part of the reserve of McDowell's force, possibly 1,000 strong. The inhabitants were, if eyes spoke truth, secessionists to a man, woman and child, and even the negroes looked extra black, as if they did not care about being fought for. A short way beyond this village, Germantown, the scene of the recent excesses of the Federalists, afforded evidence in its blackened ruins that Gen. McDowell's censure was more than needed. Let me interpolate it, if it be only to show that Gen. Beauregard and his rival are at least equal in point of literary power as masters of the English tongue: in fact, will have a sufficiently precise idea of them by conceiving a line of forts some two miles in extent, zigzag in form, with angles, salients, bastions, casemates, and every thing that properly belongs to works of the kind. The strength and advantages of this position at Manassas are very much increased by the fact that 14 miles further on is a position of similar formation, while the country between is admirably adapted to the subsistence and intrenchment of troops in numbers as large as they can easily be manoeuvred on the real battle-field. Water is good and abundant, forage such as is everywhere found in the rich farming districts of Virginia, and the communication with all parts of the country easy. Here, overlooking an extensive plain, watered by mountain streams which ultimately find their way to the Potomac; and divided into verdant fields of wheat, and oats, and corn, pasture and meadow, are the Headquarters of the advanced forces of the army of the Potomac. They are South Carolinians, Louisianians, Alabamians, Mississippians, and Virginians, for the most part; the first two, singular enough, being in front, and that they will keep it, their friends at home may rest assured. Never have I seen a finer body of men — men who were more obedient to discipline, or breathed a more self-sacrificing patriotism. As might be expected from the skill with which he has chosen his position, and the system with which he encamps and moves his men, Gen. Beauregard is very popular here. I doubt if Napoleon himself had more the undivided confidence of his army. By nature, as also from a wise policy, he is very reticent. Not an individual here knows his plans or a single move of a regiment before it is made, and then only the colonel and his men know where it goes to. There is not a man here who can give any thing like a satisfactory answer how many men he has, or where his exact lines are. for the distance of 14 miles around, you see tents everywhere, and from them you can make a rough estimate of his men; but how many more are encamped on the by-roads and in the forests, none can tell. The new-comer, from what he sees at first glance, puts down the numbers at about 80,000 men; those who have been here longest estimate his force at 40,000, 50,000, and some even at 60,000 strong. And there is the same discrepancy as to the quantity of his artillery. So close does the general keep his affairs to himself, that his left hand hardly knows what his right hand doeth, and so jealous is he of this prerogative of a commanding officer, that I verily believe, if he suspected his coat of any acquaintance with the plans revolving within him, he would cast it off.
Headquarters Department of Virginia, Fairfax Court-House, July 18.General orders, No. 18.--It is with the deepest mortification the general commanding finds it necessary to reiterate his orders for the preservation of the property of the inhabitants of the district occupied by the troops under his command. Hardly had we arrived at this place, when, to the horror of every right-minded person, several houses were broken open, and others were in flames, by the act of some of those who, it has been the boast of the loyal, came here to protect the oppressed, and free the country from the domination of a hated party. The property of this people is at the mercy of troops who, we rightly say, are the most intelligent, best educated, and most law-abiding of any that ever were under arms. But do not, therefore, the acts of yesterday cast the deepest stain upon them? It was claimed by some that their particular corps were not engaged in these acts. This is of but little moment; since the individuals are not found out, we are all alike disgraced. Commanders of regiments will select a commissioned officer as a provost-marshal, and ten men as a police force under him, whose special and sole duty it shall be to preserve the property from depredations, and to arrest all wrong-doers, of whatever regiment or corps they may be. Any one found committing the slightest depredation, killing pigs or poultry, or trespassing on the property of the inhabitants, will be reported to Headquarters, and the least that will be done to them will be to send them to the Alexandria jail. It is again ordered, that no one shall arrest, or attempt to arrest, any citizen not in arms at the time, or search or attempt to search any house, or even to enter the same without permission. The troops must behave themselves with as much forbearance and propriety as if they were at their own homes. They are here to fight the enemies of the country, not to judge and punish the unarmed and defenceless, however guilty they may be.