Hooker. My present instructions will allow me to advance no farther than Lower Marlborough.

I have the honor to be, yours, respectfully,

ROBERT COWDIN,

Colonel.

I intrusted this communication to Lieutenant Candler, of Company A. Lieutenant Candler reported to me that he saw Colonel Dwirght and had a long interview with him, in the course of which Colonel Dwight showed him all his instructions from General Sickles. Extracts from these instructions I herewith submit.

First order, early Monday morning, between 2 and 3; received between 4 and 5 a. m.:

After effecting a junction with the detachment from Hooker's brigade, you will proceed along the Patuxent and make a thorough reconnaissance of the country, moving with circumspection and with the utmost vigilance to detect the presence, in whatever force he may be, and destroying, dispersing, and capturing such of the enemy as you may be able to encounter successfully. You will lose no precaution to keep open a line of communication with the base of operations and with the detachment from Hooker's brigade.

Subsequent order, written September 11 at 8 p. m.; received September 12 (this morning):

I have received express instructions from headquarters to extend this expedition to Port Tobacco, with a view its capture and occupation. the whole force afloat might co-operate with you. I would then take 1,500 picket troops with you. Be sure and visit Frederick. I was informed of the operation of the force sent from General Hooker's brigade. It was to move down the Patuxent in conjunction with your force, which will move in the same direction.

Lieutenant Candler also reports that colonel Weight intends to move to Port Tobacco, remaining upon the west side of the river, and that he had marked out for us to take the following route: From Lower Marlborough to Huntington, from Huntington to Fredericktown, from Fredericktown to Mackall's Ferry; thence to cross the river, and form a junction at Benedict with Colonel Dwight's force, which will proceed to that point direct; thence, by different routs, to Port Tobacco. Lieutenant Candler further said that Colonel Dwight would call on me at 2 p. m. and talk the matter over.

At 2 o'clock a messenger from Colonel Dwight handed me the following communication, together with the message that Colonel Dwight was waiting on the other side of the river, and would receive me or any other person I might wish to send:

SEPTEMBER 11, 1861.

COLONEL COMMANDING FORCES FROM GENERAL HOOKER'S BRIGADE:

COLONEL: Your courier arrived here last night, as did the lieutenant I had sent out to communicate with you. As their statements did not entirely agree with each other, or with my instructions from headquarters, I detained your courier until I should have heard once more from headquarters. In order to cross your force to this side it will be necessary to use some of the larger river crafts. It seems that that means can be used as well below here as at this point; therefore I think my instructions will be best carried out by your ;moving down the river to Prince Fredericktown, on your side of the river, while I move to Benedict, on my side. There is a schooner here, which I shall have dropped down the river as we march. I shall send couriers to her for times a day with any intelligence I may have for you, and you will please to keep me notified by couriers sent often to her. If you meet any considerable force of the enemy I can easily thrown you re-enforcements,and you can cross to me at any moment I deem it necessary, if it should be necessary before you reach Prince Fredericktown. I move very slowly and carefully, and, as I hear there are cavalry of the enemy on your side, it will be necessary that you should do the same. I am not able to say certainly whom I am addressing, as your courier does not know the name of the colonel. I take it to be Colonel Cowdin, of the First Massachusetts, and I shall be happy to meet him.

I have the honor to be, colonel, your obedient servant,

WM. DWIGHT,

Colonel, Commanding Expedition.