Suddenly an idea came to her, and she scanned the heavens for Tysdell's balloon. No sight of it anywhere. Tysdell was three miles away, hidden by clouds. Nevertheless she lifted her voice and sent forth a loud cry, calling his name. Immediately the answer came, quite distinct. She explained their peril, and asked Tysdell if he could come to them. He said he would try, and questioned her where they were and what wind-currents had borne them. Carlotta told Tysdell to what height he must drop (she knew her own height by the barometer), and in a very few minutes, being able to rise and fall as he pleased, he was near the two other air-sailors, and got his balloon down by the lake-side in time to help them ashore when they struck, as presently they did. The basket splashed the water, then skipped along the surface under the drag of the balloon, and was caught finally in the arms of a tree that reached out from the bank. And the only harm done was the spoiling of Miss Aërial's best frock!
Here was a case of conversation carried on easily between two balloons a mile or so above the earth and three miles apart. But other experiments made by Mme. Carlotta show that talking between balloons may go on over much greater distances, a reach of nearly eight miles having been accomplished on one occasion near Ogdensburg, New York. The explanation of this phenomenon is perfectly simple. Each balloon, while it is speaking, acts as a huge megaphone for the other, and each balloon, while it is listening, acts as a huge sounding-board for the other; and the tighter the balloons are kept under pressure of gas, the easier it is to make these great silken horns (for such they are) throw forth and receive the messages. It should be noted that this facility for voice transmission does not exist at great heights because of the rarefied air. At a mile above earth, however, this difficulty is not presented, and it may be that a superior kind of wireless telegraphy will be introduced some day by the use of talking balloons. Why not?
III
SOMETHING ABOUT EXPLOSIVE BALLOONS AND THE WONDERS OF HYDROGEN
ONE day the professor told me about some rainfall experiments with balloons that he conducted years ago for the government. There was a theory to be tested that loud explosions at a height will make the clouds pour down water, and some gentlemen in the Department of Agriculture were anxious to set off as loud an explosion as possible, say a thousand feet up in the air. Professor Myers received this commission, and proceeded at once to Washington with a gas-balloon twelve feet in diameter.
"Don't you think that balloon is rather small?" asked one of the gentlemen.
"No," said Myers; "I should call it rather large."
The other man shook his head. "I'm afraid it won't make noise enough to test our theory."