The march to Richmond was to be made by the route from Fredericksburg. This city is on the south bank of the Rappahannock, and sixty-five miles distant from Richmond. It is connected with the latter place by a railroad, of which there is a double line nearly to Hanover Junction, twenty-three miles from Richmond. The railroad crosses the Matapony river at Milford, thirty-seven miles from Fredericksburg, and the Pamunkey, twenty-five miles from Richmond, besides a number of smaller streams. Between Falmouth, where the Federal army concentrated, and Richmond, there are two main and two minor lines of defence. The first that of the Rappahannock river. Above Falmouth its abrupt banks, which are lined with high hills, difficult of access, and its narrow fords and rocky bottom render a rapid crossing for a large force almost impossible. Below, the valley of the river expands, spreading often into spacious plains, while the winding course of the stream forms numerous necks of land, easily commanded from the north side, and giving secure crossing places, and ample ground for the formation of troops. At Fredericksburg the north commands the south bank, and much of the distance, which is a mile and a half, to the frowning hills or table land beyond. But these heights equally command this intermediate plain, and are unassailable in front except by infantry. Next in the rear, and twelve miles distant, is the line of the Po river and Stannard’s Marsh, which is hardly available except to hold a pursuing foe in check. The North Anna is about forty miles from the Rappahannock, and affords another principal line of defence. It is a deep and rapid stream, with a narrow valley. The table-land on its north bank is about one hundred feet above the bed of the river, and about one hundred and fifty feet on the south bank. The extension of its line after it turns to join the South Anna, and becomes the Pamunkey, presents scarcely less obstacles than the river itself, so well is the ground guarded by swamps and flanked by streams. The last and a minor line of defence is the South Anna river, with the southern commanded by the northern bank, and too near the North Anna for a second formation by a force that has been badly defeated. Numerous small streams parallel to the line of advance present suitable points for resistance, and protect foes attacking the line communication, while the bridges over them are weak points necessary to be securely guarded. By the 20th a considerable force had reached Falmouth. General Sumner on the next day sent a summons to surrender, which elicited a correspondence from Mayor Slaughter, showing that the town was at the mercy of the combatants, and beyond the control of the city authorities.