Williamsport, Point of Rocks, &c. I have never been at Hancock or Sir John's Run..

I have the honor to be, general, respectfully, your obedient servant,.

O. E. BABCOCK,.

Corps of Engineers.

HEADQUARTERS DIVISION,.

Frederick, Md., December 8, 1861.

Colonel LEONARD, Commanding at Williamsport:

MY DEAR SIR: Reports by way of Philadelphia represent that heavy and close cannonading was heard at Chambersburg all the afternoon in the direction of Hancock. You will ascertain, if possible, what was the occasion of the firing, and, so far as you can, the purpose of the rebels in regard to General Kelley. Do not hesitate, if he is threatened, to send him aid at once-if need be, all your force-and I will supply your place on the river upon notice of your movement. Keep us well informed of the movements in his locality, as in your own. Obtain all the information you can concerning Martinsburg, its forces, defenses, &c., and especially the lay of the land about the town..

Very truly, yours,.

N. P. BANKS,.

Major-General, Commanding Division..

P. S. - Lander's brigade will be sent to re-enforce General Kelley as soon as it arrives..

[DECEMBER 10, 1861.- For McClellan to Lincoln, in reference to forward movement, found too late for publication here, see Series I, Vol. XI, Part III.]

OFFICE CHIEF ENGINEER ARMY OF POTOMAC,.

Washington, D. C., December 10, 1861.

General J. G. TOTTEN, Chief of Engineers, &c.:

SIR: The resolution of the House of Representative of July 8, of which the following is the tenor-

Resolved, That the Secretary of War be requested to furnish this House, as soon as practicable, plans and estimates, to be prepared by the Engineer Department, for completing the defensive works on the south side of the Potomac, near this city; and also to report upon the expediency of constructing similar works of defense on the northern side of this city, with estimates for the same, so as to reduce to a minimum the number of troops required for the protection and defense of the capital-

having been submitted to me in July last, I now make the following statement:

At the time when the resolution was referred to me I was attached to the headquarters of Brigadier-General McDowell as chief engineer, and few days thereafter I was in the field engaged in the campaign of Bull Runn. Previous to this movement the army of Washington, yet weak in numbers and imperfectly organized, under General Mansfield, had crossed the Potomac and occupied the south bank from opposite Georgetown to Alexandria..

The first operations of field engineering were, necessarily, the securing of our debouches tot he other shore and establishing of a strong point to strengthen our hold of Alexandria. The works required for these limited object (though being really little towards constructing.