Martinsburgh, October 17, 1863.After the excitement incident to the anticipated Imbodenish raid had partially subsided here, our vigilant “citizen scout” reported at headquarters information in reference to the movements and whereabouts of Major Gillmore's predatory rebel band, “to villainy and to vandalism consecrate.” It appears this eminent and worthy bushwhacker had conceived a plan to destroy, on a moonless night, October fifteenth, the Baltimore and Ohio railroad bridge across Back Creek, and also to tear up generally the bridges and culverts above that point. With this intention Gillmore left his temporary encampments near a distillery, in the vicinity of Strasburgh, with his adventurous “knights of the order of rum-punch,” consisting of about forty men, including two Captains and one Lieutenant. He followed in his line of march the narrow valley west of the North Mountain range, through which peacefully meanders the clear waters of Back Creek. Now, Harry Gillmore is a thorough lady's man. That potent influence said to rule court and camp and grove controlled his movements in the present instance. En route to the point at which he intended to rendezvous until night set in, he halted to see a rebel maiden, “fair and all his fancy painted her,” and she persuaded him to linger behind in her delightful society, and to intrust the business of bridge-burning to his senior Captain — Blackford. But for this circumstance Gillmore would not now be at large, as the reader will observe presently. Leaving the Major with his Delilah, the Captain marched his men beyond the diminutive village of Tomahawk, within five miles of the railroad. He encamped — very secretly, he thought — in an almost inaccessible ravine in North Mountain. It was a capital hiding-place, covered with a thick growth of timber, and, like an African jungle, easier to get into than out of. Here the party awaited the approach of nightfall. In this lair our citizen scout discovered the gang and reported the fact at headquarters. The post commandant immediately ordered out two small detachments of cavalry from the Twelfth Pennsylvania and First New-York regiments--one commanded by Captain Henry, the other by Captain R. S. Prendergast. To Captain Prendergast, by virtue of his seniority, was intrusted the management and command of the enterprise to capture the guerrillas. A small party of infantry was also directed to march to Tomahawk, to act in conjunction with the cavalry. Captain Prendergast, accompanied by the scout, reconnoitred, unseen, the position of the rebels, and judiciously posted his cavalry force where they would entirely cut off every avenue of escape. He directed Captain Henry, with the men of the Twelfth, to occupy the road running by what is known as the “Old Stone Church,” and himself and men held the main road through Tomahawk — infantry, in the mean time, by his directions, moving upon the bushwhackers from the direction of Hedgesville, with orders to dislodge them from the mountain ravine. The infantry acted promptly. It was a complete surprise — a coup daetat; the graybacks  were thunderstruck by the unexpected presence and sudden onset of “the boys in blue.” Those of them who could get to their horses sprang into their saddles, and, with accelerated speed, fled from the ravine, only to encounter the New-York and Pennsylvania boys, who met them with sabre in hand. Others left their horses behind them and took to their heels, and ran in a style exceedingly creditable to chivalrous pedestrianism. We routed them, “foot, horse, and dragoon,” capturing nearly the entire party. Captain Blackford and four men, hatless and terribly excited, spurred their horses desperately up a steep hill-side, but were overtaken and captured by the horsemen of the First New-York. The other Captain —— Diggs, I believe they called him — with his Lieutenant, attempted to “dig out” and escape on foot, but were captured by the boys of the Twelfth, as I have been informed. We captured in all, to sum up, two Captains, one Lieutenant, twenty-five men, thirty horses, besides pistols, sabres, and other weapons of offensive war “too numerous to mention.” We have exterminated, so to speak, Gillmore's choice spirits, his select party, his picked band, his daring and reckless favorites. The fortunate result of this affair is highly creditable to the genius and enterprise of Captain Prendergast, as well as to the courage and gallantry of the officers and men of the different detachments, whose effective cooperation was so essential to the complete success of the expedition. In this connection, it affords me great pleasure to state that General Kelley's son, visiting Martinsburgh to-day, paid a fine tribute to the energy, capacity, and remarkable success of Captain Prendergast, complimenting him for thus terminating, for the present time at least, the career of so many of Gillmore's lawless and ruffianly satellites. Among the prisoners were several who were in the engagement near Smithfield with Captain Summer's company, when that gallant and lamented officer lost his life. They say Gillmore killed him, but they speak in terms of praise of his spirited conduct and bravery. Honorable and valiant in life, in death, as a warrior, he rests gloriously, peacefully, where the din of battle shall never more disturb him. “He lives in fame, that died in virtue's cause.” The prisoners frankly admitted the irregular character of their military avocations. They had speculated in horses, (stolen ones, of course,) attacked our cavalry pickets at night, carried rebel mails, aided parties running the river “blockade” with goods, burned bridges, robbed Union people, and lived on the plunder thus obtained. One of them, an Irishman, boastingly remarked that he had read the Baltimore papers daily, for some time past; another, with an inward chuckle of delight, said he had crossed the Baltimore and Ohio railroad at night three times during the past three weeks, with contraband goods; while a third jocosely added that he had purchased, with “greenbacks,” an india-rubber overcoat, which came from Goodyear's establishment in New-York City, only three weeks ago! These rebel assertions may or may not be true, but as regards “articles contraband of war,” I think there is a screw loose somewhere along the Potomac.