After the defeat at Manassas, on July 24, 1861, Professor Lowe made a free ascent, and discovered the true position of the Confederates, and proved the falsity of rumors of their advance. The organization of a regular balloon corps followed, and it was attached to McClellan’s army, and used in reconnoitering before Yorktown. The balloons were operated under heavy artillery fire, but were not injured. [Illustration: A small captive military balloon fitted for observation. A cylinder of compressed hydrogen to replace leakage is seen at F.] On May 24th, for the first time in history, a general officer--in this case, General Stoneman--directed the fire of artillery at a hidden enemy from a balloon. Later in the month balloons were used at Chickahominy, and again at Fair Oaks and Richmond, being towed about by locomotives. On the retreat from before Richmond, McClellan’s balloons and gas generators were captured and destroyed. In 1869, during the siege of a fort at Wakamatzu by the Imperial Japanese troops, the besieged sent up a man-carrying kite. After making observations, the officer ascended again with explosives, with which he attempted to disperse the besieging army, but without success. During the siege of Paris, in 1870, there were several experienced balloonists shut up in the city, and the six balloons at hand were quickly repaired and put to use by the army for carrying dispatches and mail beyond the besieging lines. The first trips were made by the professional aeronauts, but, as they could not return, there was soon a scarcity of pilots. Sailors, and acrobats from the Hippodrome, were pressed into the service, and before the siege was raised 64 of these postal balloons had been dispatched. Fifty-seven out of the 64 landed safely on French territory, and fulfilled their mission; 4 were captured by the Germans; 1 floated to Norway; 1 was lost, with its crew of two sailors, who faithfully dropped their dispatches on the rocks near the Lizard as they were swept out to sea; and 1 landed on the islet Hoedic, in the Atlantic. In all, 164 persons left Paris in these balloons, always at night, and there were carried a total of 9 tons of dispatches and 3,000,000 letters. At first dogs were carried to bring back replies, but none ever returned. Then carrier pigeons were used successfully. Replies were set in type and printed. These printed sheets were reduced by photography so that 16 folio pages of print, containing 32,000 words, were reduced to a space of 2 inches by 1¼ inches on the thinnest of gelatine film. Twenty of these films were packed in a quill, and constituted the load for each pigeon. When received in Paris, the films were enlarged by means of a magic lantern, copied, and delivered to the persons addressed. [Illustration: