WASHINGTON, D. C., January 15, 1862.

Major General H. W. HALLECK,

Commanding Department of Missouri, Saint Louis:

My letter of 3rd was not intended to direct or advise you to strip Missouri of troops so as to endanger the safety of the State. It was only to indicate to you the objects in view and to obtain your views, as well as to learn what troops you had dispensable for the movement. I wrote on 13th fully. Shall I forward mortars for rafts and how many? Have new arms arrived and how many more do you need?

GEO. B. McCLELLAN,

Major-General, Commanding.

HEADQUARTERS THIRD BRIGADE, January 15, 1862.

General THOMAS:

SIR: Colonel Wolford has returned from a scout. He says that he went to Harrison; from there to the Wolf Creek road; then to Logan's; from there 4 miles down the Mill Springs road; then back.

He says that he saw nothing, and could hear nothing, and that there were no pickets on any of the roads over which he went; that there were no horse-tracks on the roads made since the rain. This would seem to indicate that Zollicoffer had departed, if it were not for other reliable news just received by me from one whom I sent out this morning. Old man Foster says that last night the enemy came in very considerable force, some three regiments, on the McLennan Hill, situated between Forbush and Wolf Creek, about 1 mile from the river. This afternoon the whole body took back towards their camp by way of the road between Forbush and White Oak (Robertsport road). They were compelled to go what way on account of the river having risen.

This evening at sundown they were passing toward White Oak Creek, within 8 miles from their camp, whipping and pressing their arms very hard. They are now out of our way, I think. What a nice thing we have missed by not having means of getting news! Now, I hardly think that he could have come out to attack us, or they would not have brought the wagons. This would look as though he had not known of our presence until to-day, and then he took back. I will have my advance and pickets keep a sharp lookout should an attack be contemplated.

If he comes this way we can whip all of them without any trouble in the position we have.

I send you this that you may take such steps as seem proper.

I have no news from the camp of the enemy other than what you are in possession of. I am about satisfied that he has not to exceed 5,000, all told. I will give you the particulars when I see you.

Yours, truly,
R. L. McCOOK.

P. S.-I think we could not intercept the train now, as we would have to go by the Mill Springs road to head them off, a march of 16 miles.