We take the following highly interesting account of the Battle of South Mountain, fought Sunday last, from the New York Times. It was furnished by its special correspondent: ON THE BATTLE FIELD, Sunday Night, Sept. 14, 1862.

Although the battle of today was of long duration, still it was not so sanguinary, considering the forces engaged, as a spectator would at first be inclined to suppose. Our loss in killed and wounded will not probably exceed 2,000, and that I judge to be a high estimate.

Since Gen. Pleasonton's brigade of cavalry advanced from Rockville, we have had skirmishes daily along the route. During those skirmishes the enemy's force consisted of about two regiments of cavalry and two or three pieces of artillery. On Saturday, however, more regiments of cavalry were added, making a force equal, if not superior to our own.

The force that opposed our advance until today was the rear guard of the enemy, and the battle ground of yesterday was evidently selected with a view of staying our further progress.

The Battle Ground.

The first division to enter the field on our side was Cox's, of Reno's Corps. Next came the Pennsylvania Reserve Corps, Ricketts' and King's Divisions, under command of the gallant and brave Hooker. We had batteries stationed on both wings, but at no time was there over ten or twelve pieces in practice.

The enemy's force is supposed to have amount to about 40,000 men. He probably used twelve pieces of cannon. The forces of Gen. Longstreet and D.H. Hill were engaged.

The Battle.

The rebel position was on the summit and sides of the Blue Ridge Mountain on each side of the gap, known as Frog Gap [Turner's Gap], through which the main road on the turnpike from Middletown to Hagerstown passes. The Gap is distant from Middletown about three miles, and from Frederick twelve miles.

Boonsboro, the next important town to Middletown on the turnpike, is two miles from the gap, on the other side of the mountains. The mountains in the vicinity of the Gap are steep and rugged, and rendered difficult to ascend unless by the ordinary thoroughfares, on account of numerous ledges and loose rocks which afford no permanent foothold.

From base to top they are covered with a thick wood, thereby giving protection to the party in possession, and making the progress of the attacking force doubly hazardous.

Bolivar, a village boasting of five or eight dwellings, is situated on the main road, between Middletown and the Gap, and about one and a half miles from the latter place. At Bolivar, a road branches off from each side of the main road, the two roads taking a circuitous course to the mountains and gradually ascending them, join the main road again at the Gap.

The early position of the Union army, or where the line of battle was first formed, was on a piece of rising ground on the right and left of the main road between Bolivar and the mountains.

As the day advanced and our forces moved forward, the position was changed, but never for the better. The nearer we approached the mountains, the more successfully could the enemy bring his artillery to bear on our columns. No matter what position we held, the Blue Ridge mountains commanded that position. It will be observed at once, that the enemy had a formidable ground of defense, and nothing but undaunted courage wrested it from him.

The Forces Engaged.

The battle commenced with artillery at 7 a.m. Robertson's U.S. Battery of four light field pieces firing the first shot.

This battery was stationed about six hundred yards to the left of the turnpike, the fire being directed at no particular place, but with a view of shelling the woods generally, so as to draw a reply from the rebels.

The firing was continued for over an hour, but the enemy did not respond until Cox's division appeared in the main road, advancing to take a position.

Two pieces stationed in the Gap were then opened upon the column. The troops, however, turned into a field at the left of the road, and got out of harm's way before any injuries were effected. Here they remained in line of battle for an hour and a half. In the meantime the enemy's position having been discovered, Robertson directed the fire of his pieces to the Gap. Soon after the rebels opened another battery at the right of the Gap, and subsequently still another battery at the left.

It was then evident that the rebels intended to make a vigorous stand on the mountain. Since the preceding day they had brought up extra pieces of cannon, for, as before stated, they had used but three, at the most, in the skirmishes during the week. The enemy was now firing from nine pieces, consequently, to make a vigorous reply, Hayne's U.S. Battery of six pieces moved up to the left to the assistance of Robertson.

A heavy cannonading then ensued, but, as usual in artillery duels, little damage was effected on either side. At 10 a.m. the enemy withdrew his pieces on the left and right of the Gap, and worked principally with those in the Gap. A half an hour later all of the enemy's guns were silent, but upon the moving of Cox's division soon after to the edge of the woods on the side of the mountain at the left, the rebels again produced their pieces at the right of the Gap.

Cook's Massachusetts Battery of six pieces was now brought up to support Robertson's, and a concentrating fire was poured into the Gap, many of the shells bursting directly over the rebel guns. At first the enemy threw solid shot, but after a while changed his projectile to shell.

Three times during the day the rebels were forced to change the position of their pieces, and late in the afternoon their guns were silent altogether.

By 11 o'clock Cox's division had arrived at the woods, and a few minutes later had entered for the purpose of getting around the enemy's right. At this juncture Generals McClellan and Burnside, with their staffs, rode upon the field, where they remained during the continuance of the battle.

Cook's Battery took a favorable position for shelling the woods in advance of the division, but had hardly got to work when the rebels fired a tremendous volley of musketry at the cannoniers. This was repeated several times in quick succession, until at length the cannoniers abandoned their pieces, and ran to the rear, leaving four or five of their comrades dead upon the ground. The drivers of the caissons also partook of the panic and dashed headlong through the ranks of Cox's Division, which was drawn up in line of battle a few yards to the rear.

Two companies of a cavalry regiment, which were supporting the battery, also galloped through the line of infantry, thus leaving four pieces of artillery (the other two having been detached to another part of the field) to fall into the hands of the enemy. The event caused temporary, and only temporary, confusion among the troops. They quickly straightened the line and prepared to resist a demonstration observable on the part of the enemy to seize the abandoned pieces.

The rebels march forward to secure their anticipated prize, and at the same moment the Twenty-third Ohio and One Hundredth Pennsylvania Regiments advanced in splendid order to repulse them.

Each side seemed desperate in its purpose, and the struggle was most exciting. At length the Forty-fifth New York came to the rescue and turned the tide of fortune in our favor. Both parties suffered severely in the action. The rebels retreated in great confusion, while our men made the woods resound with cheers.

For the succeeding two hours the infantry under the command of Reno ceased operations, and the artillery alone continued the duel. The guns used thus far were 6, 10 and 12-pounders. Simmons' Ohio battery of four 20 pounders were now placed in position on the left and commenced throwing shells to the right of the Gap, at which point the rebels had again stationed a battery.

The firing for a while was exceedingly animated, but the 20 pounders proved too much for the rebels, and they were compelled, in the course of half an hour, to change the position of their guns. At the expiration of the next half-hour their guns were silenced.

In this battle the enemy did not appear to have so many guns as usual, or if he did have them, he did not bring them into practice. The 30 pounder, which he was so fond of using against us on the Peninsula, did not make its appearance here.

At 3 p.m. the head of Gen. Hooker's column appeared coming up the turnpike to reinforce Reno. The column took the road branching off from the turnpike at the right, near Bolivar, and proceeded to the foot of the mountains. All along the line the utmost enthusiasm was manifested for Hooker. Every man in the corps was evidently impressed with the belief that he had a General willing and able to lead them forward in the face of the enemy.

At 3 p.m. the line of battle from right to left was formed in the following order, near the base of the mountains on the right, and at the edge of a piece of woods on the mountain slope at the left: The First brigade of Ricketts' division on the extreme right, which was about one mile north of the turnpike; the Pennsylvania reserve corps, the right resting on Ricketts' left; the Second regiment, United States sharpshooters on the road branching off from the turnpike at the right; the Second and Third brigades of Ricketts' division between the branch road and the turnpike; King's division, (commanded by Genral Hatch) at the left of the turnpike, the right resting on the turnpike; Gen. Reno's force on the extreme left, about a mile and a half from the turnpike.

The Sixth United States, Eighth Illinois, Eighth, Third and Twelfth Pennsylvania, Sixth New York, Third Indiana and First Massachusetts cavalry regiments were on different portions of the field performing picket duty, acting as guards to the roads and supporting batteries.

Up to this time all our batteries had been stationed to the left of the turnpike, as the positions secured there enabled the gunners to work their pieces to advantage.

About one hundred yards in the rear of the Pennsylvania Reserve Corps was stationed Captain Cooper's First Pennsylvania battery of four pieces; Captain Ransom's, company C, Fifth United States battery, of four pieces, took a position at the extreme right, in the rear of the first brigade of Ricketts' division.

Immediately after the line of battle was formed, the right, left and center commenced moving simultaneously toward the enemy on the slopes of the mountains.

The rebels opened on the column with two pieces of cannon, directing the fire of one to the right, and of the other to the left of the line. They were replied to by one of Simmon's 20 pounders on our left, and Cooper's battery on our right. The enemy continued the firing for upward of an hour, when, on account of the severe punishment he was receiving from our guns, and the near approach of our infantry to his pieces, he disappeared on the other side of the mountain.

The enemy's shells for the most part went over the Union troops, consequently they did not effect much damage.

Steadily onward went our long, unbroken line of infantry, until the right wing had gained a piece of woods on the mountain, a short distance from the base, when the Bucktails, who were skirmishing on the right, discovered the enemy's pickets.

A desultory rattling of muskets was next heard, which indicated the commencement of the battle on the part of the infantry. The column form the right to left still remained unbroken, and advanced firmly but cautiously up the steep. In a short time the enemy's main force was encountered, and then came heavy volleys of musketry on the right. The Pennsylvania Reserve Corps and the First Brigade of Ricketts' Division were now hotly engaging the enemy.

The rebels stood their ground for awhile, but after a contest of thirty minutes they wavered, and commenced falling back in disorder toward the summit of the mountains. Our forces pushed them vigorously, and kept up a continuous fire.

The valor displayed on this occasion by the Pennsylvania Reserves, and the corps formerly under the command of McDowell, is deserving of the highest praise. Not a straggler could be seen on the field. Every man was at his post in the line. They all seemed determined to force back the enemy and take possession of the mountains spite of any opposition that might be placed in their way.

General Hooker, accompanied by his staff, was where he always is on such occasions - at the front. The line did not give way for an instant, but kept moving forward and upward, pouring volley after volley of musketry into the enemy's ranks, until at last the rebels broke and ran precipitately to the top of the mountain - thence down the other side.

Reno's corps on the left did its part nobly. The men were called upon to do some severe fighting, and they performed their duty with a will and heroism seldom before displayed. The engagement on the left succeeded that on the right, and lasted about an hour and a half. The enemy contested every foot of ground, but eventually yielded it to the conquerors.

The centre column was the last to come into the action. The same success that marked the advance of the two wings also attended the centre. At 6 p.m., after an engagement of three hours' duration, the rebels fled, leaving the top of the mountain in the possession of the Union troops. Darkness prevented us from pursuing the enemy further at the time.

The Result.

The result of the battle secures to the Union troops a vert important position, inasmuch as it commands the approaches on each side of the mountain, also a vast area of the surrounding country. I estimate, as before stated, that two thousand will cover the list of our casualties. I think that the enemy's loss in killed and wounded will not exceed our own. altogether we captured two thousand prisoners. Gen. Reno was killed on the field of battle. At the time of the calamity he was observing, by aid of a glass, the enemy's movements. He was struck in the spine by a musket ball -- the ball lodging in the breast.

A correspondent of the New York Tribune, writing from Middletown, Md., on Sunday, says:

The rebels, in leaving Middletown yesterday, burned a splendid barn containing 2,000 bushels of wheat and 60 tons of hay, belonging to Adam Kooglas, a wealthy planter and strong Union man. They also destroyed a fine bridge across Middle Creek, a few steps from his house. Three or four shells from our batteries passed through the mansion of Mr. Kooglas. One lodged in the bed in a room occupied by one of his daughters, but fortunately did not explode. The shell in now the most prominent parlor ornament.

A bold attempt was made last evening to burn the jail in Frederick and release about 500 prisoners confined there. The alarm was sounded about 11 o'clock, and in less than ten minutes the Tenth Maine Cavalry, Colonel Allen, who had unsaddled and gone to rest, were on their horses and surrounding the jail. The jail was of stone, with the exception of the roof and cross timberings. Not one of the prisoners, notwithstanding many desperate attempts, succeeded in escaping. The Ninth New York, Fire Zouaves, were on the ground a few moments after the Maine Cavalry, and took great delight in subduing their old enemy.

General Garland.[From The Sun's edition of Sept. 17, 1862]

The Confederate General Garland, who is reported to have been killed in the battle near Hagerstown, Md., on the 14th instant, is Robert E. Garland, late captain of the Seventh United States infantry, and is understood to be a son of the late Brig. Gen. John Garland, colonel of the Eighth infantry, one of the heroes of the Mexican war.General Robert E. Garland was a native of Virginia, but was appointed from Missouri to a second lieutenancy in the Seventh infantry, on the 30th of December, 1847.

His commission as a first lieutenant dated from March 3d, 1853. He was a regimental quartermaster in 1858, and in 1861 rose to a captaincy in the same regiment, a position he did not hold many months, as, having given evidence of his disloyalty while with his regiment in New Mexico, he was ordered to be dropped from the roles of the army, to date May 23d, 1861.

General McClellan's Staff: Chief of staff, Brigadier General Randolph B. Marcy; Adjutant General, Brigadier General Seth Williams; Inspector General, Colonel Delos B. Sackett; Chief Quartermaster, Colonel Rufus Ingalls; Chief Commissary, Col. Henry F. Clark; Medical Director, Dr. Jonathan Letterman; Chief of Ordnance, Lieutenant Horace Porter; Aides-de-Camp, Lieutenant Colonel Edward McR. Hudson, Lieutenant Colknel Nelson B. Sweetzer, Lieutenant Colonel Albert V. Colburn; Chief Topographical Engineer, vacant; Chief Engineer, vacant.