The main road to the arsenal is by a wide and vacant avenue, which abuts against a gate where automaton sentries walk, but the same gate can best be reached on foot by the shores of the Potomac, in the sight, of the forts, the shipping, and Alexandria. The scene at the arsenal in time of peace is common-place enough, except that across the Eastern Branch the towers of the lunatic asylum, perched upon a height, look down baronially; but this trial of murderers has made the spot a fair. A whole company of volunteers keeps the gate, through which are passing cabs, barouches, officers' ambulances, and a stream of folks on foot; while farther along almost a regiment crosses the drive, their huddled shelter tents extending entirely across the peninsula. These are playing cards on the ground, and tossing quoits, and sleeping on their faces, while a gunboat watches the river front, and under a circular wall a line of patrols, ten yards apart, go to and fro perpetually. It is 10 o'clock, and the court is soon to sit. Its members ride down in superb ambulances and bring their friends along to show them the majesty of justice. A perfect park of carriages stands by the door to the left, and from these dismount major-generals' wives, in rustling silks; daughters of congressmen, attired like the lilies of the milliner; little girls who hope to be young ladies and have come with "Pa," to look at the assassins; even brides are here, in the fresh blush of their nuptials, and they consider the late spectacle of the review as good as lost, if the court-scene be not added to it. These tender creatures have a weakness for the ring of manacles, the sight of folks to be suspended in the air, the face of a woman confederate in blood. They chat with their polite guides, many of whom are gallant captains, and go one after another up the little flight of steps which leads to the room of the officer of the day. He passes them, if he pleases, up the crooked stairways, and when they have climbed three of these, they enter a sort of garret-room, oblong, and plastered white, and about as large as an ordinary town-house parlor. Four doors open into it--that by which we have entered, two from the left, where the witnesses wait, and one at the end, near the left far corner, which is the outlet from the cells. A railing, close up to the stairway door, gives a little space in the foreground for witnesses; two tables, transverse to this rail, are for the commission and the press, the first-named being to the right; between these are a raised platform and pivot arm-chair for the witness; below are the sworn phonographers and the counsel for the accused, and then another rail like that separating the crowd from the court, holds behind it the accused and their guards.