In reply, I beg leave to report that, upon my arrival at Hagerstown, on the night of the 19th instant, I was ordered by Brigadier-General Reynolds, U. S. Volunteers, in command of Pennsylvania militia, to move out to the Williamsport road with my brigade, and report to him. I complied with the order, and them reported my arrival to your headquarters, from which I received orders to join General Couch's division, at Williamsport. The enemy was at this time (Saturday, the 20th instant) in the town,and General Reynolds directed me to remain in line of battle between Hagerstown and Williamsport. On Sunday, the 21st, learning that a portion of Major-General Franklin's army corps were in this town, I sent in and reported to Major-General Franklin, from whom I received orders to march here to relieve Colonel Rush's command, to hold and occupy the town, and to defend the ford over the Potomac. I was placed in command here by his orders, and have endeavored to obey his instructions. Several changes have been made in the disposition and number of the troops here since yesterday, and my force now consists, first, of several battalions of my own brigade, say, 1,600 men; second, eight guns Maryland battery, Company A, Captain Wolcott, 120 men; third, seven companies of the Twelfth Illinois Cavalry, Colonel Voss commanding, 350 men; fourth, two independent companies Maryland cavalry, commanded by Captains Russell and Graffin, 100 men.

Under instructions from Major-General Franklin, received during last night, I have ordered a regiment of infantry to Clear Spring, 9 miles from here, on the road to Hancock; a section of artillery and a squadron of cavalry to Dam No. 5, distant 5 or 6 miles up the river; a squadron of cavalry to Hancock, to watch the fords from there down to Dam No. 5, and the balance of the cavalry I am using, to the best of my judgement, in guarding the fords near to and the roads leading to the town. One battalion of my infantry is supporting the battery posted on the heights, to the left of the town, and the balance doing duty in and about the town. I have no troops whatever in Hagerstown, except detachments which I left there to guard my subsistence, ammunition, and camp and garrison equipage, all of which I was forced to leave there when I marched, as I have not one single wagon, no transportation whatever having been furnished me, except that on yesterday I borrowed a few wagons to bring down some subsistence. I am now hard at work endeavoring to subsist my command.

After receiving your note of yesterday, I immediately ordered Colonel Voss to send a squadron of his cavalry to Hagerstown, but I have learned since that the Eight New York Cavalry were there, which was detached or ordered away from here on yesterday, and countermanded the order.

I will forward you a proper return of my brigade as soon as I can make it out. I have given you a rough aggregate, which, I hope, may answer at present.

One full regiment of my brigade (the Sixth Maryland) and four pieces of artillery, Captain Alexander's battery, attached to my command, I learn are at the Monocacy Junction, Baltimore and Ohio Railroad, where they were been detained, as I understand, by orders from Major-General Wool. It would add materially to the strength and morale of my brigade to have them with me. All is comparatively quiet here and above. A strong picket of the enemy is posted immediately opposite the town, on the river bank at the ford.

I have the honor to be, very respectfully, your obedient servant,

JOHN R. KENLY,

Brigadier-General Vols., Commanding at Williamsport.