3rd. It can be let up into the air by means of a rope in a calm day to a height sufficient to observe the country for twenty miles around and more, according to the degree of clearness of the atmosphere. The ascent may also be made at night and the camp lights of the enemy observed.

4th. From experiments made here for the first time it is conclusively proved that telegrams can be sent with ease and certainly between the balloon and the quarters of the commanding officer.

5th. I feel assured, although I have not witnessed the experiment, that when the surface wind is from the east, as it was for several days last week, an observer in the balloon can be made to float nearly to the enemy's camp (as it is now situated to the west of us), or even to float over it, and then return eastward by rising to a higher elevation. This assumption is based on the fact that the upper strata of wind in this latitude is always flowing eastward. Mr. Lowe informs me, and I do not doubt his statement, that he will on any day which is favorable make an excursion of the kind above mentioned.

6th. From all the facts I have observed and the information I have gathered I am sure that important information may be obtained in regard to the topography of the country and to the position and movements of an enemy by means of the ballo Mr. Lowe is well qualified to render service in this way by the balloon now i.

7th. The balloon which Mr. Lowe now has in Washington can only be inflated in a city where street gas is to be obtained. If an exploration is required at a point too distant for the transportation of the inflated balloon, an additional apparatus for the generation of hydrogen gas will be required. The necessity of generating the gas renders the use of the balloon more expensive, but this, where important results are required, is of comparatively small importance.

For these preliminary experiment, as you may recollect a sum not to exceed $200 or $250 was to be appropriated, and in accordance with this Mr. Lowe has presented me with the inclosed statement of items, which I think are reasonable, since nothing is charged for labor and time of the aeronaut.

I have the honor to remain, very respectfully, your obedient servant,

JOSEPH HENRY,

Secretary Smithsonian Institution.

On the evening of the 21st of June I received a telegram from Captain Whipple, of the Topographical Engineers, directing me to fill the balloon and to bring it, with the telegraphic apparatus, &c., to Arlington.

The gas could not be obtained from the Washington Gas Company until the following afternoon, when the balloon was inflated and taken across the Long Bridge to Arlington House, where, by order of Captain Whipple, it remained until the next morning at 4 o"clock, when I was ordered to take it to Falls Church. On arriving at the Alexandria and Loudoun Railroad I learned from the guards that there were no pickets out in the direction we were going. There being no other route by which the balloon could be towed, on account of the woods, and knowing the importance of observations from Falls Church, the balloon was let up by ropes to a sufficient height to ascertain that it was safe to proceed. We then advanced two miles farther, to Bailey's Cross-Roads, where I was informed by the residents that a rebel scouting party had just left, having seen the balloon, and supposing that a large force accompanied it. After stopping a few minutes we proceeded to Falls Church, where the balloon was kept in constant use for two days more, during which time General Tyler sent up an officer who sketched a fine map of the surrounding country and observed the movements of the enemy. Captain Whipple and other officers also made several ascensions.

On the 26th of June I was informed by Captain Whipple that the Bureau of Topographical Engineers had concluded to adopt the balloon for military purposes, and desired me to furnish a full account of the method of operating the balloons in the field, and to make estimates for their construction, &c. The information I gave he