OFFICE OF CHIEF ENGINEER, ARMY OF THE POTOMAC, Washington, February 1, 1862.

Colonel A. V. COLBURN,.

Assistant Adjutant-General:

COLONEL: In compliance with the wishes of the Commander-in-Chief, communicated through you, I, in company with Captain Duane, engineer, had an interview with General Banks in reference to the means of crossing his army over the Upper Potomac. He stated that his orders were to be prepared to cross at short notice, to operate against the heavy columns of the enemy in Winchester Valley and westward, and appeared to be impressed with the idea that a bateau bridge (or, in other words, such a bridge equipage as we have provided for the Army of the Potomac, for it amounts to this) was important and indispensable. I expressed my convection that to cross a river like the Potomac at this season, to encounter an enemy who has the power to make himself superior, on an ordinary pontoon bridge, which may be swept away in twenty-four hours or less, that for a great many reasons, which I need not introduce here, I considered Haper's Ferry the best place to cross, and whether that was selected as the place or not it must be held, and a brigade communication kept up there; that canalboat and materials (according to Lieutenant Babcock's statement) could be easily accumulated there, and that a bridge could be established in forty- eight hours; that if other secure crossings were wanted above, they must be established after the passage of our armies; and, finally, that if circumstances should distance to him a passage at another point, I believe a flying bridge made of two canal-boats could be promptly established, would be comparatively secure, and would passes a capability of carrying over troops nearly equal to a bateau bridge..

Should these reasons not appear satisfactory, and a bateau bridge be decided necessary, and that to be capable of transportation, so that the point of passage may be selected or changed at will, then we can only meet the demand by ordering an equipage of fifty boats, with wagons and teams (100), and with it should be sent one or two companies of engineer troops. To build such an equipage would require three or four weeks, and it could not be supplied in shorter time unless the general chooses to send some of the equipage already provided. General Banks' idea of the economy of resorting to a bateau bridge was founded upon an imperfect idea of what was necessary to constitute one.

The general left me, saying he would consider the subject further.

Captain Duane coincides with me in these views.

I am, very respectfully, &c.,

J. G. BARNARD,

Chief Engineer.

GENERAL ORDERS,
HDQRS. OF THE ARMY, A. G. O.,

Numbers 9.
Washington, February 1, 1862.

I. The States of Pennsylvania and New Jersey are added to the limits of the Department of the Potomac.

* * * *

By command of Major-General McClellan:

L. THOMAS,

Adjutant-General.