Gen. McCook Censured — Fears Entertained that Burnside may be Cut Off.

[Times' Special.]

WASHINGTON, Sept. 25. — It appears now that all three of Rosecrans' grand divisions were engaged in the battles in front of Chattanooga, of which two were driven back in considerable disorder. Gen. Rosecrans, in his dispatches, imputes the loss of the battle to disobedience of orders on the part of Gen. McCook, who failed to occupy an important position assigned him by Rosecrans. Had he done as ordered, Rosecrans' opinion is that the battle would have resulted in a splendid Union victory. By extending his forces too much, the enemy were enabled to penetrate Rosecrans' lines.

Great anxiety is felt here in army circles for the safety of Burnside. In order to reinforce Rosecrans, his only safe course would be to cross the Tennessee river and move down between the river and the mountains, or to penetrate to some of the gaps and move down behind the mountains. The opinion of military men seems to be that if he attempted to move down this side of the river, he would run great risk of being cut off.

[Special to the Tribune.]

CINCINNATI, Sept. 25. — In the course of the day, the 17th, already unmistakable signs were indicated that the enemy had discovered the weak points of our position, and were massing their forces in front of our left center and left for the purpose of crushing those parts of our lines, or getting between them and Chattanooga.

On the morning of the 18th (Friday) a portion of the expected reinforcements, consisting of two brigades of the reserve corps, respectively commanded by Colonels McCook and Mitchell, made their appearance near Chattanooga, and were immediately ordered to make a reconnoissance towards Ringgold and develope the intentions of the enemy from that quarter. They came upon the advance of Longstreet's corps and pushed it back for some distance, took a number of prisoners from it, and fully established the anticipated concentration of the enemy in front of our left. All day Friday cavalry, covering our front, skirmished with different bodies of the enemy.

On Friday night, the divisions of Brannan and Baird, together with Johnson's and McCook's corps, moved from the rear to the left of Crittenden's corps. They were in their new positions at daybreak. The two other divisions of McCook's corps (Davis' and Sheridan's) were to move into the position abandoned by Thomas' corps, but had not time to assume it fully before the commencement of the action. Next morning, the early forenoon passed away without a forewarning of the approaching conflict, but shortly before eleven o'clock, the storm that had been brewing all morning on the rebel side, burst forth in the expected direction. At that time a long mass of rebel infantry was seen advancing upon Brannan's division, on the extreme left. It first came upon the 2d brigade, Col. Croxton commanding, and soon forced it back, despite its determined resistance. The two other brigades of the division at once came to its assistance, and succeeded in checking the progress of the rebels and driving them back, but their column being in turn heavily reinforced they advanced again with wild yells. So powerful was this assault that they pushed Brannan back to and behind his position in the line, and thus uncovered the left of Baird's division. Making prompt use of their advantage, they changed their course to the left and speedily enveloped Scribner's and King's brigades, the latter regulars. They were almost surrounded, but managed to disentangle themselves.

After a fearful loss the rebel masses next came upon Johnson's division and rolled it upon Reynolds, which also became speedily involved in the struggle of the resistance to these divisions. A sweeping fire of some batteries posted under the personal supervision of Gen. Reynolds, arrested at last their advance. The division of Brannan and Baird having been rallied, Gen. Thomas ordered a general advance of the right, and soon the tide of the battle decidedly turned in our favor. With cheers our line advanced, halting only at times to shatter the enemy with musketry. Several times they were driven from position to position, and by four o'clock all the ground lost was nearly recovered. Several batteries belonging to Gens. Baird's and Brannon's divisions, whose horses had been killed and supports swept away, were retaken, and several hundred prisoners captured. The enemy left all their dead and nearly all their wounded on the field. There were at least 500 of the former. The rebel troops engaging Thomas belonged to Buckner's and Longstreet's command. At the time the struggle was turning in our favor on the left, Bragg's army property consisting of the corps of Polk and Hill, formerly Hardee's, moved to a most determined and well executed attack upon Palmer's and Van Cleve's division in the centre. Its object obviously was to relieve the rebel right. Palmer and Van Cleve soon found themselves overpowered and their divisions breaking. Their complete rout was imminent when Davis' division came to their support on Van Cleve's right. Timely reinforcements at first had the effect of checking the enemy and restoring our line, but the rebel attack was speedily renewed with greater numbers, and the centre again compelled to yield. Davis was forced to the right and Van Cleve to the left, and the enemy advanced through the opening in our line, threatening to take the centre, and aided by their flanks as they had done on the left.

At this critical juncture Sheridan's division appeared, and was at once thrown upon the enemy. It stood its ground gallantly for a while, but becoming soon exposed to a destructive flank fire, was also compelled to fall back. Fortunately the divisions of Gens. Wood and Negley that had been early withdrawn from Gordon's Mills when the rebel attack on our left threatened to be successful, now came to the rescue. After a brief contest the rebels found themselves at last matched and commenced giving way in their turn. Reynolds, having also been sent to the assistance of the centre after the repulse of the rebel right, and advance was ordered, and our original position regained about sunset. About dark the enemy made another demonstration, with a heavy artillery and musketry fire on our center, but eliciting a lively response, they soon abandoned this last effort of the day, and thus ended the battle of the 19th.

CINCINNATI, Sept. 26. — Yesterday's Nashville Union says Burnside has reached the point where he was expected to prevent the flank movement of the enemy.

Col. Wilder, of Rosecrans' cavalry, who has arrived at Nashville, reports matters at the front much more favorable than is believed north.

NEW YORK, Sept. 26. — According to the correspondence of the Tribune, it appears that previous to the battle McCook" corps reached Alpine, twenty-eight miles northwest of Rome on the 10th. Thomas' corps encountered the enemy in strong force in the valley between Mission and Pigeon Mountains, on the 11th, and fell back to Mission Ridge. On the 17th Crittenden's corps connected with Thomas. Rosecrans ordered McCook to fall back to the main force, which he accomplished on the 15th. Decerters on the 16th and 17th reported the arrival of Longstreet's corps at Recra Station, near Lafayette, which determined Rosecrans, in the face of the numerical superiority of the rebels, to be attacked in his own chosen position, rather than seek the enemy.

WASHINGTON, Sept. 23. — The Republican says the government has received glorious news from Rosecrans, but the details cannot be dated. The rebel army, from the latest telegrams, has not, it appears, molested Rosecrans in his present position. There is in Washington a general spirit of cheerfulness regarding further military operations.