CAIRO, ILL., September 4, 1861.

GENERAL: Information is just in from Sikeston, which I am disposed to credit, although the authority is a negro man. He tells a very straight story. Says that the rebels left Sikeston last Monday; had there four regiments of Tennessee and Mississippi troops, ten or twelve pieces of artillery drawn by horses, one large piece drawn by five yoke of oxen, and one mortar drawn by three yoke. In addition to this Jeff. Thompson had 1,500 men. They said they were going to New Madrid and then to Memphis.

On the strength of reconnaissance made by Colonel Waagner I telegraphed this evening that troops-artillery, cavalry, and infantry- can be spared from here by sending those from Jackson promptly to take possession of Columbus Heights, and New Madrid will fall within five days after. This should be done to-morrow night. Inclosed I send you the report of Commander Rodgers [Numbers 5.], retaining copy.

Respectfully, your obedient servant,

U. S. GRANT,

Brigadier-General, Commanding.

Major General JOHN C. FREMONT,

Commanding Dept. of the West, Saint Louis, Mo.

HEADQUARTERS WESTERN DEPARTMENT,
Saint Louis, Mo., September 5, 1861.

Brigadier General U. S. GRANT, Cairo, Ill.:

You will commence and prosecute with the utmost speed all the preparation of the place selected for the fort and entrenched camp on the Kentucky shore, forming a triangle with Cairo and Bird's Point, which fortification we will call Fort Hilt. The point, if not determined now, should be defined by Colonels Waagner and Webster, and Lieutenant Freeman, who was especially intrusted with eh selection of the spot. To protect the place and the work to be done there you will order a sufficient force of infantry, cavalry, and artillery, selecting the troops, according to your own judgment, from Cape Girardeau, Cairo, and Bird's Point, and replacing them from our forces concentrated at Jackson. The force employed on the Kentucky shore should number at least six regiments of infantry, two squadrons of cavalry, and a battery of artillery, and only after the force is there and the place secured against attack will you plant the four heavy guns to be brought by Captain Schwartz. Besides one of the two artillery companies organized by Colonel Waagner, you will detach all the artillerists of Colonel Smith's regiment of Zouaves to Fort Holt; and, using the sand-bags at Cairo and the gabions going with the guns, and employing day and night the largest force of workmen obtainable, you will put the place in a state of defense in the shortest possible time.

The ammunition called for by requisition of Captain Brinck, acting ordnance officer at Cairo, will be sent to-morrow. If you feel strong enough, you will take possession of Paducah; but if not, then opposite that place, on the Illinois side of the river, which you will do without delay, with the view of planting a battery which shall command the Ohio and the mouth of the Tennessee River. In a few days I will send an adequate force with sufficient artillery to hold that position. If in your power, it would be well to make preparation for building a bridge to connect the Illinois shore with Paducah.