So far as I am informed, the medical staff belonging to the different volunteer regiments discharged their duties satisfactorily. I observed Acting Assistant Surgeon Miles busily engaged in dressing wounded men under the shade of a tree in a part of the field where the fire from the enemy was very hot. He addressed me a brief inquiry as I passed relative to the safety of his farther, and then resumed his occupation. Surg. C. C. Keeney, of Colonel Hunter's division, and Assist. Surg. D. L. Magruder, attached to the commanding general's staff, did good service in the hospital church I have mentioned, and also in two houses near the church, where the wounded wee placed after the church had been filled. These officers remained busily engaged int he discharge of their duties still the enemy's cavalry made their appearance, and but narrowly escaped capture when they left. Drs. Swift and Winston, attached to the New York Eighth, remained with their sick, sacrificing all selfish considerations for their own safety in order that the wounded might not be neglected, and are ow prisoners. I am informed that Assistant Surgeons Gray and Sternberg, of the Regular Army, and Drs. Homiston and Swalm, of the New York Fourteenth, also preferred to remain rather than abandon their charge. The conduct of these officers is worthy of all commendation.

It would be premature in me, in the absence of sufficient date-the reports of the regimental surgeons not yet being received-to express a positive opinion as t the number killed and wounded in the action on the 21st. There were, no doubt, many concealed from observation under cover of the woods and bushes; but, judging from the number that I saw in various parts of the field, and allowing a wide margin for those unobserved, I should think that the killed and wounded on our side did not exceed from 800 to 1,000.

The impossibility of making a careful survey of the field after the battle had ceased must be my apology for the briefness and want of detail in this report.

W. S. KING,

Surgeon and Medical Director, U. S. Army.

Captain J. B. FRY,

Assistant Adjutant-General, U. S. Army, Arlington, Va.

Numbers 15. Report of Major William F. Barry, Fifth U. S. Artillery, Chief of Artillery.

ARLINGTON, VA., July 23, 1861.

CAPTAIN: Having been appointed, by Special Orders, Numbers 21, Headquarters Department Northeastern Virginia, Centreville, July 19, 1861, chief of artillery of the corps d'armee commanded by Brigadier-General McDowell, and having served in that capacity during the battle of 21st instant, I have the honor to submit the following reports:

The artillery of the corps d'armee consisted of the following-named batteries: Ricketts' light company, I, First Artillery, six 10-pounder Parrott rifle guns; Hunt's light company, M, Second Artillery, four light 12-pounders; Carlisle's company, E, Second Artillery, two James 13-pounder rifle guns, two 6-pounder guns; Tidball's light company, A, Second Artillery, two 6-pounder guns, two 12-pounder howitzers; Greene's company, G, Second Artillery, four 10-pounder Parrott rifle