Doc. 159.-General Onderdonk's expedition.
Acting Brigadier-General B. F. Onderdonk has just returned to this point from an extended and most successful raid up to the very gates of Richmond. The start of this expedition was made at one o'clock P. M., on the twenty-sixth of August, from  Williamsburgh. After a quiet march, of little interest to the general reader, we halted and encamped at Twelve Mile Ordinary. On the morning of the twenty-seventh we moved forward without molestation ; but at Slatersville we met a strong picket, whose insolent and defiant action would lead one to suppose that the enemy was in their rear in large supporting force. Colonel Onderdonk accordingly ordered a charge to be made on the force in our front, whatever it might be, and the result was, that they were chased in the most gallant style by our men a distance of two miles. One man of the rebels was killed, and two more captured, the rest escaping by reason of their fresh horses, which of course could distance our jaded animals. Proceeding further, when we arrived at New-Kent Court-House we were opposed by another, picket. Two of these were captured, but we failed, for the former reason, to come up with the rest, although the most strenuous efforts were made to that effect by our forces, which consisted of the First New-York Mounted rifles and the Fifth Pennsylvania cavalry, the whole under command of Colonel Onderdonk, of. the rifles, who, in his capacity of acting Brigadier, had fall powers delegated him to act in the premises as he pleased, although the orders were explicit in writing not to go further than New-Kent Court-House. Verbal orders were, however, obtained, at the solicitation of Colonel Onderdonk, to the effect that we might move forward in the enemy's country as far as might be deemed prudent and safe in the mind of the commanding officer. Accordingly, with his customary dash, the Colonel commanding placed his own gallant regiment in the advance, and moved on to Baltimore Store, where one rebel picket was captured, and the rest retired in accelerated time. There was no delay; so on we dashed without a pause to Crump's Cross-Roads, where we met the enemy in force of about some thirty well mounted troopers. Of course a charge was in order, and our men, inflated with success, went plunging after the rebels, who quickly fled in the direction of Bottom's Bridge, up to which point we pursued them, making in all a continued chase of three miles. The rifle-pits and earthworks of the enemy on the other side of the bridge were found to be quite formidable, and opened heavily on us the moment we appeared. In this furious affair the impetuosity of our troops was highly praised by all observers. Indeed the scene was splendid. Imagine a thousand troopers, brave, bold, and well trained, with staring eyes, determined looks, and flashing sabres, dashing down, with screams and yells, upon the foe. This was indeed one worthy of the pen and brain of Longfellow. The loss of the enemy in this affair, we learned from authentic sources, was thirty killed and wounded. The Mounted rifles, who took the most active part in this fight, by their conduct exemplified to me what I never in my experience in the army could understand before — namely, a total unconsciousness of danger, and an apparent contempt for death. McClellan's earthworks on the Richmond side of Bottom's Bridge had, it seems, been so altered by the rebels that they could most effectually resist our advance. These works are upward of six feet high, very strong, and defended by five hundred infantry and a squadron of cavalry. General Wise, with a force of four thousand men, was reported by contrabands to be lying in wait for us two miles further on toward Richmond, beyond the bridge; so Colonel Onderdonk thought it prudent, considering his explicit written orders, to retire, having done much more than was required of him by his commanding officer. The return was at once made to Baltimore Store, where we encamped. Our position here was very strong indeed, and was selected with the view of repulsing any movement the enemy might make against us in the night. General Wise, it was ascertained, did actually cross to attack us, but, finding us in strong position, re crossed again before morning. A pursuit was begun on the twenty-eighth by the enemy, who attempted to cut us off at New-Kent Court-House or Slatersville, but all in vain. At noon on this day we halted at Slatersville to feed our horses and refresh ourselves. There the enemy charged suddenly on the Fifth Pennsylvania cavalry, creating quite a panic on our surprised men; but the Mounted rifles came to the rescue in most gallant style, and charging with irresistible fury upon the presumptuous foe, drove him in confusion a distance of four miles, inflicting severe punishment on him meantime. The enemy's force was, in all, five hundred effective men, consisting of Holcomb's Legion of South-Carolina troops, and the Fifth Virginia. In this splendid counter-charge of our troops we killed a major, an orderly sergeant, and two privates, and wounded fifteen men. On the twenty-ninth we returned to Williamsburgh, and were sent immediately to this point. The national loss was very slight, we having only one killed and two wounded, whose names are as follows: Killed.--John Noetting, Fifth Pennsylvania cavalry, troop A. Wounded.------Riley, Fifth cavalry, troop I; Corporal Fitzpatrick, Fifth cavalry, troop I. The captures were not immense, but important. At New-Kent Court-House a civilian named O. M. Chandler was taken into custody b Colonel Onderdonk, and sent to Fortress Monroe. When the rebel pickets fled before us this man misled our officers, by wilfully stating that they took the road to the left, when he knew that they were on that to the right. By this means the greater portion escaped, and for this falsehood Chandler lost his liberty. Another arrest of a citizen was made by the Colonel at Baltimore Store, where Mr. Elmore, an employe of the rebel government, was seized and carried off. The plunder in the shape of horses, equipments, etc., was not as large as usual; but the poverty of the country accounts for this. We captured a set of telegraph instruments, however, and a good quantity of horses, besides destroying  a rebel army wagon, direct from Richmond, loaded with rifles. Of course their destruction was made complete, inasmuch as we could not carry them off with us. The result of this affair is most satisfactory, and Colonel Onderdonk has received the encomiums of his commanding officers and all qualified for gallant actions. The conduct of the Mounted rifles was splendid, and well sustained their old reputation. All the troops, in fact, engaged in this raid acted with unsurpassed gallantry.