SEDALIA, Mo., December 7, 1861.

General HALLECK, Headquarters:

No news from the cavalry, but I apprehned to disaster. Sent an express to-day, which will probably return to-morrow evening. This afternoon, as our teams were out a few miles from camp north of Georgetown, for hay, the men were attacked by rebels and disarmed.

The teams and men are safe. An irregular mounted force and some infantry in wagons were sent in pursuit. We frequently perceive the want of cavalry. Mr. Allen, from Lexington, states that nearly everybody in that part of the State has gone to join Price, and it is believed there Sedalia will be attacked in a few days. I have spies watching the movements of the enemy.

FRED'K STEELE,

Colonel, Commanding.

GENERAL ORDERS,
HDQRS. DEPT. OF THE MISSOURI, Numbers 19.
Saint Louis, Mo., December 7, 1861.

I. The mayor of the city of Saint Louis will require all municipal officers to immediately subscribe to the oath of allegiance prescribed in the ordinance passed by the Convention of this State on the 16th day of October, 1861.

II. The provost-marshal-general will take measures to ascertain whether any civil officer of this State fails within the time fixed by said ordinance to subsribe and file the oath there prescribed, and any person having failed to take such oath, who attempts to exercise civil authority in violation of the terms of said ordinance, will be arrested.

* * * * *

By order of Major-General Halleck:

J. C. KELTON,

Assistant Adjutant-General.

SYRACUSE, Mo., December 8, 1861.

Major-General HALLECK:

News that Price has crossed the Osage not yet confirmed. Detachment sent to Warsaw will be in to-day. Are the disposition of troops and the selection of my headquarters approved? First and Second Division in position at La Mine to-day.

JNO. POPE,

Brigadier-General.

SYRACUSE, Mo., December 8, 1861.

Major-General HALLECK:

Steen's division of Price's force crossed the Osage three days since, and scattered along the river above and below Osceola. Price on south side. Steen's return of his force show 8,000 men. It is undoubtedly his purpose to scatter most of his forces in counties adjoining the Osage, on north side, for subsistence. One battalion of Steen's divisions descended the river towards Warsaw. If it be deemed necessary to keep Price's force on south side of Osage, our advance in force towards Clinton will be necessary.

JNO. POPE,

Brigadier-General.