I am gratified to be able to transmit this statement of General McClellan's, as I certainly understood his letter of the 18th instant as an accusation of a grave character against this Department, and as such an swered it, I trust, satisfactorily.

As no copy of General McClellan's letter of the 18th instant was retained in this office, I request that a copy may be furnished for the records.

I am, very respectfully, your obedient servant,

M. C. MEIGS,

Quartermaster-General.

HDQRS. INSPECTOR OF ARTILLERY, U. S. ARMY, Washington, October 23, 1862.

Colonel J. C. KELTON,
Assistant Adjutant-General, Headquarters of the Army:

COLONEL: The breaking down of a very serviceable mounted battery in a recent cavalry reconnaissance to the Rappahannock (wherein it is stated that 60 miles were marched in twenty-four successive hours), affords the opportunity to offer a few suggestions, which I beg respectfully to present to the consideration of the General-in-Chief. I would recommend that whenever artillery is required upon cavalry reconnaissances, batteries, or parts of batteries, of horse artillery only be used. The organization of the ordinary mounted batteries of the service does not adapt them to the rapid and long-sustained marches of cavalry, and they must, whenever so used, be either broken down or rendered unserviceable for many weeks. If one field battery in each army corps is organized and equipped as horse artillery, these will ordinarily be a force of this special arm sufficient for all cavalry operations. In the event of batteries of horse artillery not being at hand, or not available at the moment, for this special service, I offer the following recommendations to adapt temporarily the mounted batteries for rapid movement:

1st. Detail, for the occasion, a sufficient number of horses from the cavalry upon which to mount the cannoneers.

2d. March without caissons, or, at most, with only the caisson limber. The first (which on many accounts is preferable) would give 50 rounds per gun, which would ordinarily be sufficient; the latter, 100 rounds per gun, a supply amply sufficient for any circumstances likely to attend such special service. I think too large a force of artillery is generally taken upon cavalry reconnaissances. A force of 1,200 or 1,500 cavalry will not require more than one section (two guns), unless it be intended to divide the forces and march upon two roads, when two sections (four guns) should be taken. In no case, however, if artillery is used at all, should less than two guns be taken.

I am, colonel, very respectfully, your obedient servant,

WILLIAM F. BARBY,

Brigadier-General and Inspector of Artillery.

WAR DEPARTMENT, Washington City, October 23, 1862.

Major-General HALLECK,

General-in-Chief:

GENERAL: The inclosed telegram from Governor Curtin is referred