ARLINGTON, VA., September 16, 1861.

Brigadier General F. J. PORTER,

Commanding Division at Fort Corcoran:

SIR: In accordance with your request I herewith send a statement of what I should advise and deem necessary in addition to the means now at hand for the purpose of facilitating and making more frequent reconnaissance with balloons, and from various points at the same time, also for the purpose of being ready to accompany the army whenever a movement is made.

First. An addition of two balloons would be required, with capacities as follows: One of 30,000 cubic feet and one of 20,000 built of the best India silk and linen cordage, with all my late improvements and appliances. The cost of these air vessels complete will be, for the largest, $1,500; the smallest, $1,200.

Secondly. A portable inflating apparatus would be required for the purpose of inflating a balloon at any point where common, gas cannot be obtained, and also for the purpose of replenishing the balloons when the gas is partially expended. This would save the expense of an entire reinflation, and also keep the balloon ready for observation at all times; besides, the hydrogen being more buoyant than local gas, a greater altitude can be obtained.

The whole cost of this apparatus ought not to exceed $500, and can be built by ship carpenters and coppersmith now in the employ of the Government at Washington. The time required for getting up these balloons and apparatus will be about two weeks, perhaps less, should the weather prove fine while coating the material.

By being supplied with the above additional equipments I feel confident in being able to keep the Government constantly informed of the movements and position of the enemy, as well as the topography of the country. Wherever occasion requires, the balloons can also be used for letting up various colored signal lights at night, which can be made to burn for a long time, and consequently will be seen with more certainly than by any other meatfully, yours,

T. S. C. HEADQUARTERS, September 20, 1861.

Brigadier General F. J. PORTER,

Commanding Division, Fort Corcoran:

DEAR SIR: I have just taken an observation from an altitude of 1,000 feet, and find the atmosphere uncommonly clear in the west. I shall move to the place where you first ascended, and would be pleased if you can come and go up with me. We may be able to discover something of interest.

Very respectfully, your obedient servant,

T. S. C. LOWE.

BALLOON HEADQUARTERS, September 22, 1861.

Brigadier-General PORTER,

Commanding Division, Fort Corcoran:

During my observation this evening I noticed a pretty heavy picket force on Upton's Hill and several camp smokes at Taylor's Corners. On the west slope of Munson's Hill there appeared to be a full regiment with a set of colors, their bayonets glistening in the sun as if on parade. I could see nothing of the horses you spoke of, but as soon as I can get the balloon inflated again I will go nearer and examine the woods.

Very respectfully, yours,

T. S. C. LOWE.

CAMP ADVANCE, September 23, 1861.

General F. J. PORTER:

At about 8.30 to-morrow morning I wish to fire from here at Falls Church. Will you please send the balloon up from Fort Corcoran and have note taken of the position reached by the shell, and telegraph each observation at once.

W. F. SMITH.

HEADQUARTERS PORTER'S DIVISION,
Fort Corcoran, Va., September 24, 1861.

Professor LOWE:

SIR: By direction of General Porter I herewith inclose a telegram from General Smith. It explains itself. Two mounted orderlies will be sent you so that you can, with the assistance of your officer, report and send to these headquarters.