A train of ambulances was sent, by consent of the rebel commander, to bring in our wounded. About 700 arrived last night. The officers who went with the flag of truce to negotiate this, report the rebel officers courteous, thought they carefully excluded them from their lines, and admitted the ambulances only on condition that on leaving our picket-lines, they should be driven by their own people. Escaped prisoners report the rebel soldiers as saying among themselves that a few more such battles will kill them all off; others asserting that the Yankees can never subjugate them, and being answered by their comrades that the Yankees are killing them off pretty fast. The pickets up the river say they intend to give General Rosecrans two days to surrender; if he refuses, to thrash him. There are indications of a large force on both sides of the Mission Ridge, which is east of the town. A general's headquarters, apparently, i at a house on the crest of the ridge, and there are numerous camp-fires on the ridge and in the valley beyond.

What they may attempt it is not possible to predict, but I think their great effort of concentration has failed. The United States holds Chattanooga, and, I believe, will hold it. As a fortified base, it threatens the south and southwest. I have telegraphed to Cincinnati for wrought-iron pipe and force-pumps to supply water to a fort erected on Cameron's Hill, which will be of most difficult approach, and will command the greater part of the town and serve as a citadel when General Rosecrans leaves this place. It will be an intrenched camp of great strength, though without masonry escarps. It will be built entirely by the labor of this army. Two sawmills left in good condition by the rebels are being run by the pioneers, sawing out lumber for bridges, boats, and fortifications. A large foundry was partly dismantled, but its flasks and some of the machinery remain, and its buildings are uninjured. They are used as a smith's shop. Much wrought and cast iron remains. There are the truss-bolts of some destroyed bridge, and the rim of an enormous fly-wheel intended for a rolling-mill. At this foundry the machinery for rolling-mills has been made. The rebels carried off much machinery when they fled, but a large quantity of property useful to the army was left, and is seized, inventoried, and used for military purposes.

I see little evidence of plunder on the part of the troops, who are sober, orderly, and well behaved, and do credit to the nation by their courage in the field, their endurance on the march, their patience and cheerful labor, and their conduct in this guilty town. Garden fences and all other obstructions to free passage suffer, of course, but of wanton destruction I see none.

M. C. MEIGS,

Quartermaster-General.

CHATTANOOGA, TENN., October 3, 1863-8.20 p.m. [Received 12 m.,4th.]

Hon. E. M. STANTON,

Secretary of War:

The destruction of the train by rebels yesterday makes it more necessary that the trains of the troops coming from the east may be forwarded after them with all dispatch. Lieutenant-Colonel Mackay, chief of General Thomas' corps, has visited the scene, and re-