CAMP NEAR FALMOUTH, VA., April 21, 1863.

Captain C. B. COMSTOCK,

Chief of Engineers, Army of the Potomac:

CAPTAIN: In answer to yours of this date I would respectfully say that all of the balloons, with the exception of the two now i use (needing repairs that could not readily be done in the field), were sent to Washington the 17th with the balloon badge and old generators, which also need repairs. The balloons were sent to the Columbian Armory, where they have always been taken for repairs or storage, there being a large room for that purpose.

I intended for balloons to be kept in readiness for this army, and that two should be sent with the aeronaut that goes South, in order that he may operate with economy and to advantage. As to repairs to the balloons, it will be impossible to state exactly what they are until they are thoroughly examined. the principal. things, however, for the two that Intended for the South are turning inside out, recrating, and inserting new top and valve in one of them.

As to the two aeronauts, of whom you desire me to name the one best qualified to be placed at the disposal of the War Department, I would state tha, for that service neither of them would answer, by an experienced army aeronaut who has had experience in the management of balloons for war purposes, which is quite different from the art practiced in the ordinary way. Therefore if you do not desire to send the aeronaut first named by me, under all the circumstances I would most respectfully ask to be order to report to the Secretary of War in his stead. With this arrangement the wishes of the Honorable Secretary could be complied with, and at the same time all machinery could be kept in order for all points where balloons are used.

I remain, very respectfully, your obedient servant,

T. S. C. LOWE,

Aeronaut.

CAMP NEAR FALMOUTH, VA., April 22, 1863.

Captain C. B. COMSTOCK,

Chief of Engineers, Army of the Potomac:

CAPTAIN: I examined the enemy's position more closely this p. m., between 4 and 6 o"clock, than I have had an opportunity of doing for a number of days past. If I might be permitted to venture an opinion as to the relative strength of the enemy, I should say that they are about three to our four. I should estimate their supports to the batteries immediately back of the city of Fredericksburg to be about 10,000.

Immediately opposite where General Franklin crossed, say from two to three miles from the river, and from the railroad station along the height about one mile and half, I should say that there were 25,000 troops camped.

Still farther to the left and south of the railroad there are also several large camps. During the time I was up I noticed many regiments on parade, near the various camps, and at one place there were three, while still farther back, I should judge four miles from the river and one mile to the left of the railroad, I saw a column of infantry moving to the right which required about twenty minutes to pass a given point, after I discovered them, and I counted what I took to be seven regiments. They had no colors flying as those did that were on parade.

Should the morning be fine I shouto ascend with you, and could then better explain the points refnclined to believe that the enemy are either strengthening their army or bringing up their troops from Bowling Green and the Junction. The latter is the most probable, as there is not as much smoke visible in that direction as heretofore.

Very respectfully, your obedient servant,

T. S. C. LOWE,

Chief of Aeronautics.

On the 27th General Butterfield ordered me to make frequent ascensions, and to report to him and to General Sedgwick. Captain Comstock was then absent, and I did not see him until the 6th of May.

The following orders and reports relative to observations during the seven-days" battle I think worthy of special attention, as they show what can be done by the balloons when required, and they