HEADQUARTERS GENERAL CASEY'S DIVISION,
Poplar Hill, June 8, 1862.

Captain C. C. SUYDAM,

Assistant Adjutant-General, Fourth Corps:

CAPTAIN: A communication from Headquarters Army of the Potomac, under date of May 23, 1862, has been referred to me, desiring "an explanation in detail of the extraordinary falling off in the effective strength of Casey's division since March 30, 1862."

I had been furnished with a copy of this letter several days ago, and at once made a report to you, a copy of which was handed to Major Davis, assistant inspector-general on the staff of the major-general commanding.

In compliance with further directions from your headquarters, I had caused detailed reports to be rendered from the several brigades of my command, which were lost in the battle of the 31st ultimo, in common with the other books and papers of this division.

The material for a report in detail is no longer in my possession. I can only refer to my former report and to the monthly returns from my brigades, now nearly ready for transmission, as conveying all the information in my power to give.

Very respectfully, your obedient servant,

SILAS CASEY,

Brigadier-General Volunteers, Commanding Division.

[Indorsement.]

JUNE 9, 1862.

Respectfully submitted to Headquarters Army of the Potomac.

Among the reasons for the falling off in Casey's division are, in my opinion:

1st, and principal. There were eight raw in that division, and the troops had less opportunity for instruction and organization than the troops that fought at Bull Run.

2nd. Until the division left Washington there was but one brigadier 3rd. Great sickness, owing principally to unwholesome encampments and partly to a lack of sufficient military experience and vigilance on the part of officers.

4th. Think there has been a feeling of discouragement in that division, in which there are many excellent men, growing out of the impression, true or false, that the division has not been held in high repute.

E. D. KEYES,

Brigadier-General, Commanding Fourth Division.

CAMP IN THE REAR, June 17, 1862.

Brigadier General S. WILIAMS,

Assistant Adjutant-General, Army of the Potomac:

GENERAL: The action of General McLellan in regard to my communication to you of the 4th instant was not communicated to me until the 14th.

I would respectfully request you send to me at your earliest convenience a copy of the dispatches sent by General Heintzelman and others to General McLellan upon which he based his dispatch to the Secretary of War on the 1st of June respecting the battle of Fair Oaks, that