supplying them. I have a cavali from Smith's Point to Port Tobacc pickets along the shores of the I' Cape Lookout. They may not be the Potomac; this I cannot expect feat the plans of many.

I have nothing new to report of
Very respectfully, your ob

Brige

e line) were nevertheless, considering the small number of ailable, arduous undertakings. Fort Corcoran, with its auxil*, Forts Bennett and Haggerty, and the block-houses_and parapets around the head of the Aqueduct, Forts Runyon, JackAlbany (covering our debouches from the Long Bridge), and lsworth, on Shooter's Hill, Alexandria, were mostly works of mensions. During the seven weeks which elapsed between the gof the Potomac and the advance of General McDowell's army gineer officers under my command were so exclusively occupied These works (all of which were nearly completed at the latter date), make impracticable the more general reconnaissances and studies ssary for locating a line of defensive works around the city and paring plans and estimates of the same.

The works just mentioned on the south of the Potomac, necessary the operations of an army on that shore, were far from constituting defensive system which would enable an inferior force to hold the ong line from Alexandria to Georgetown or even to secure the heights of Arlington.

On the retreat of our army such was our situation. Upon an inferior and demoralized force, in presence of a victorious and superior enemy, was imposed the duty of holding this line and defending the city of Washington against attacks from columns of the enemy who night cross the Potomac (as was then deemed probable) above or below.

Undecided before as to the necessity, or at least the policy, of surrounding Washington by a chain of fortifications, the situation left no longer room to doubt. With our army too demoralized and too weak in numbers to act effectually in the open field against the invading enemy, nothing but the protection of defensive works could give any degree of security. Indeed, it is probable that we owe our exemption from the real disaster which might have flowed from the defeat of Bull Run-the loss to the enemy of the real fruits of his victory-to the works previously built (already mentioned), and an exaggerated idea on his part of their efficiency as a defensive line.

The situation was such as to admit of no elaborate plans nor previously-prepared estimates. Defensive arrangements were improvised and works commenced as speedily as possible where most needed. A belt of woods was felled through the forest in front of Arlington and half-sunk batteries prepared along the ridge in front of Fort Corcoran and at suitable points near Fort Albany, and a battery of two rifled 42pounders (Battery Cameron) was established on the heights near the distributing reservoir above Georgetown to sweep the approaches to Fort Corcoran.

Simultaneously a chain of lunettes (Forts De Kalb, Woodbury, Cass, Tillinghast, and Craig) was commenced, connecting Fort Corcoran and the Potomac on the right with Fort Albany on the left, and forming a continuous defensive line in advance of the heights of Arlington. The wooded ridge which lies north of and parallel to the lower course of Four Mile Run offered a position from which the city, the Long Bridge, and the plateau in advance of it could be overlooked and cannonaded. While our external line was so incomplete, it was important to exclude the enemy from its possession. Access to it was made difficult by felling the forest which covered it (about 200 acres), and the large lunette (Fort Scott) was commenced as soon as the site could be fixed (about the middle of August). The subsequent establishment of our defensive line in advance throws this work into the same category with Forts Corcoran, Albany, Runyon, &c., as an interior work, or second line, but it

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 Representatives 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 a few days thereafter I was in the field engaged in the campaign of Bull Run. 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 secur ing of our debouches to the other shore and establishing of a strong point to strengthen our hold of Alexandria. The works required for these limited objects (though being really little towards constructing

a defensive line) were nevertheless, considering the small number of troops available, arduous undertakings. Fort Corcoran, with its auxil iary works, Forts Bennett and Haggerty, and the block-houses_and infantry parapets around the head of the Aqueduct, Forts Runyon, Jackson, and Albany (covering our debouches from the Long Bridge), and Fort Ellsworth, on Shooter's Hill, Alexandria, were mostly works of large dimensions. During the seven weeks which elapsed between the crossing of the Potomac and the advance of General McDowell's army the engineer officers under my command were so exclusively occupied with these works (all of which were nearly completed at the latter date), as to make impracticable the more general reconnaissances and studies necessary for locating a line of defensive works around the city and preparing plans and estimates of the same.

The works just mentioned on the south of the Potomac, necessary for the operations of an army on that shore, were far from constituting a defensive system which would enable an inferior force to hold the long line from Alexandria to Georgetown or even to secure the heights of Arlington.

On the retreat of our army such was our situation. Upon an inferior and demoralized force, in presence of a victorious and superior enemy, was imposed the duty of holding this line and defending the city of Washington against attacks from columns of the enemy who might cross the Potomac (as was then deemed probable) above or below.

Undecided before as to the necessity, or at least the policy, of surrounding Washington by a chain of fortifications, the situation left no longer room to doubt. With our army too demoralized and too weak in numbers to act effectually in the open field against the invading enemy, nothing but the protection of defensive works could give any degree of security. Indeed, it is probable that we owe our exemption from the real disaster which might have flowed from the defeat of Bull Run—the loss to the enemy of the real fruits of his victory-to the works previously built (already mentioned), and an exaggerated idea on his part of their efficiency as a defensive line.

The situation was such as to admit of no elaborate plans nor previously-prepared estimates. Defensive arrangements were improvised and works commenced as speedily as possible where most needed. A belt of woods was felled through the forest in front of Arlington and half-sunk batteries prepared along the ridge in front of Fort Corcoran and at suitable points near Fort Albany, and a battery of two rifled 42pounders (Battery Cameron) was established on the heights near the distributing reservoir above Georgetown to sweep the approaches to Fort Corcoran.

Simultaneously a chain of lunettes (Forts De Kalb, Woodbury, Cass, Tillinghast, and Craig) was commenced, connecting Fort Corcoran and the Potomac on the right with Fort Albany on the left, and forming a continuous defensive line in advance of the heights of Arlington. The wooded ridge which lies north of and parallel to the lower course of Four Mile Run offered a position from which the city, the Long Bridge, and the plateau in advance of it could be overlooked and cannonaded. While our external line was so incomplete, it was important to exclude the enemy from its possession. Access to it was made difficult by felling the forest which covered it (about 200 acres), and the large lunette (Fort Scott) was commenced as soon as the site could be fixed (about the middle of August). The subsequent establishment of our defensive line in advance throws this work into the same category with Forts Corcoran, Albany, Runyon, &c., as an interior work, or second line, but it

is nevertheless an important work, as, taken in connection with Forts Richardson, Craig, &c., it completes a defensive line for Washington independent of the extension to Alexandria.

The defense of Alexandria and its connection with that of Washington was a subject of anxious study. The exigency demanding immediate measures, the first idea was naturally to make use of Fort Ellsworth as one point of our line, and to connect it with Fort Scott by an intermediate work on Mount Ida. An extended study of the topography for several miles in advance showed that such a line would be almost indefensible. Not only would the works themselves be commanded by surrounding heights, but the troops which should support them would be restricted to a narrow space, in which they would be overlooked and harassed by the enemy's distant fire. The occupation of the heights a mile in advance of Fort Ellsworth, upon which the Episcopal Seminary is situated, seemed absolutely necessary. The topography proved admirably adapted to the formation of such a line, and Forts Worth and Ward were commenced about the 1st of September, and the line continued simultaneously by Forts Blenker and Richardson to connect with Forts Albany and Craig. Somewhat later the work intermediate between Blenker and Richardson-filling up the gap and having an im portant bearing upon the approaches to Forts Ward and Blenker and the valley of Four Mile Run-was commenced.

The heights south of Hunting Creek, overlooking Alexandria and commanding Fort Ellsworth, had been always a subject of anxiety. The securing to our own possession the Seminary Heights, which commanded them, diminished materially the danger. As soon, however, as a sufficient force could be detached to occupy those heights and protect the construction of the work it was undertaken, and the large work (Fort Lyon) laid out and commenced about the middle of September.

Previous to the movement of the army defensive measures had been taken at the Chain Bridge, consisting of a barricade (bullet proof, and so arranged as to be thrown down at will) across the bridge, immedi ately over the first pier from the Virginia side, with a movable staircase to the flats below, by which the defenders could retreat, leaving the bridge open to the fire of a battery of two field guns immediately at its Maryland end, and a battery on the bluff above (Battery Martin Scott) of one 8-inch sea-coast howitzer and two 32-pounders. As even this last battery was commanded by heights on the Virginia side, it was deemed proper, after the return of the army, to erect another battery (Battery Vermont) at a higher point, which should command the Virginia Heights and at the same time sweep the approaches of the enemy along the Maryland shore of the Potomac.

During the months of May and June the country between the Potomac and the Anacostia had been examined mainly with the view of obtaining knowledge of the roads and defensive character of the ground, not in reference to locating field defenses. At the period now in question there was apprehension that the enemy might cross the Potomac and attack on this side. Of course what could be done to meet the emergency could only be done without that deliberate study by which a complete defensive line would best be established. The first directions given to our labors were to secure the roads, not merely as the beaten highways of travel from the country to the city, but also as in general occupying the best ground for an enemy's approach.

Thus the sites of Forts Pennsylvania, Massachusetts, Slocum, Totten, Bunker Hill, Saratoga, and Lincoln were rapidly chosen, and works commenced simultaneously at the first, second, third, and sixth of these