In the mean time the destruction of the batteries on the Lower Potomac, by crossing our troops opposite them, was considered, and preparations were even made for throwing Hooker's division across the river, to carry them by assault. Finally, however, after an adverse report from Brigadier General J. G. Barnard, chief engineer, given below, who made a reconnaissance of the positions, and in view of the fact that it was still out of the power of the Navy Department to furnish suitable vessels to co-operate with land troops, this plan was abandoned as impracticable. A close examination of the enemy's works and their approaches, made after they were evacuated, showed that the decision was a wise one. The only means, therefore, of accomplishing the capture of these works, so much desired by the President, was by a movement by land, from the left of our lines, on the right bank of the Potomac-a movement obviously unwise.

The attention of the Navy Department, as early as August 12, 1861, had been called to the necessity of maintaining a strong force of efficient war vessels on the Potomac:

HEADQUARTERS DIVISION OF THE POTOMAC, Washington, August 12, 1861.

SIR: I have to-day received additional information which convinces me that it is more than probable that the enemy will, within a very short time, attempt to throw a respectable force from the mouth of Aquia Creek into Maryland. This attempt will probably be preceded by the erection of batteries at Mathias and White House Points. Such a movement on the part of the enemy, in connection with others probably designed, would place Washington in great jeopardy. I most earnestly urge that the strongest possible naval force be at once concentrated near the mouth of Aquia Creek, and that the most vigilant watch be maintained day and night, so as to render such passage of the river absolutely impossible.

I recommend that the Minnesota and any other vessels available from Hampton Roads be at once ordered up there, and that a great quantity of coal be sent to that vicinity, sufficient for several weeks' supply. At least one strong war vessel should be kept at Alexandria, and I again urge the concentration of a strong naval force on the Potomac without delay.

If the Naval Department will render it absolutely impossible for the enemy to cross the river below Washington, the security of the capital will be greatly increased.

I cannot too earnestly urge an immediate compliance with these requests.

I am, sir, very respectfully, your obedient servant,
GEO. B. McCLELLAN,

Major-General, Commanding.

Honorable GIDEON WELLES, Secretary of the United States Navy.

It was on the 27th of September, 1861, that General Barnard, chief engineer, in company with Captain Wyman, of the Potomac flotilla, had been instructed to make a reconnaissance of the enemy's batteries as far as Mathias Point. In his report of his observations he says:

Batteries at High Point and Cockpit Point, and thence down to Chopawamsic, cannot be prevented. We may, indeed, prevent their construction on certain points, but along here somewhere the enemy can establish, in spite of us, as many batteries as he chooses. What is the remedy? Favorable circumstances, not to be anticipated nor made the basis of any calculations, might justify and render successful the attack of a particular battery. To suppose that we can capture all, and by mere attacks of this kind prevent the navigation being molested, is very much the same as the suppose that the hostile army in our own front can prevent us building and maintaining field works to protect Arlington and Alexandria by capturing them, one and all, as fast as they are built.

In another communication upon the subject of crossing troops for the purpose of destroying the batteries on the Virginia side of the Potomac General Barnard says:

The operation involves the forcing of a very strong line of defense of the enemy and all that we would have to do if we were really opening a campaign against them there.