HEADQUARTERS OF BALLOON, September 25, 1861.

Brigadier-General PORTER,
Commanding Division, Fort Corcoran:

SIR: Soon after you departed I heard the report of three guns toward Chain Bridge. I ascended and remained up until 12 o"clock, during which time no more guns were fired. About three miles in advance of Chain Bridge I could distinguish the glistening of bayonets and quite a large body of men, in motion, but as they were going from the bridge I concluded they were General Smith's forces.

The parade at the Seminary made a grand display, while on Munson's Hill quite a large crowd were gathered. After descending I heard two more guns in the direction of the Chain Bridge, but the wind has arisen and prevents me from taking any observation at present. I am confident that there is no great movement on the part of the enemy, or I should have seen something of it, although the distance and heavy smoke are great obstacles to-day in that direction.

Very respectfully, your obedient servant,

T. S. C. LOWE.

QUARTERMASTER-GENERAL'S OFFICE,

Washington City, September 25, 1861.

Prof. T. S. C. LOWE:

(In care Major S. Van Vliet, senior quartermaster, Army of the Potomac, Washington.)

SIR: Upon the recommendation of Major-General McClellan the Secretary of War has directed that four additional balloons be at once constructed under your direction, together with such inflating apparatus as may be necessary for them and the one now in use. It is desirable that they be completed with the least possible delay.

Very respectfully, your obedient servant,

M. C. MEIGS,

Quartermaster-General.

On the 30th of September the balloon was taken to Upton's Hill and used constantly, General McDowell, the Count de Paris, and other officers ascending with me and gaining much valuable information greatly needed at the time, as there was no other means of learning the position and movements of the enemy, and where an attack was expected. I received many complimentary remarks during the day from the officers, who were satisfied of the value of the balloon for reconnaissance.

From the 1st to the 12th of October the balloon was left in charge of an assistant while I was engaged in the construction of the balloons and gas generators ordered by the Secretary of War.

QUARTERMASTER-GENERAL'S OFFICE,

Washington City, October 1, 1861.

Lieutenant Colonel G. H. CROSMAN,

Deputy Quartermaster-General, Philadelphia, Pa.:

COLONEL: The Secretary of War having authorized Professor Lowe to construct four balloons for military purposes, you will pay for them, and such bills as may be made by him in their construction, the whole amount to be paid being about the sum he names as their cost, viz, for the two largest $1,500 each, and for the smallest $1,200 each.

Very respectfully, your obedient servant,

By order:

E. SIBLEY,

Brevet Colonel, U. S. Army, Deputy Quartermaster-General.

GENERAL McCLELLAN'S HEADQUARTERS,

Washington, October 12, 1861.

Professor LOWE:

General McClellan directs that you report yourself to General Smith at Johnson's Mill. Be there sure to-morrow, Sunday night.

A. V. COLBURN.

In accordance with the above order I inflated the balloon the same evening and started at 9 p.m. Our progress was slow, the night