Page:My Airships.djvu/122

 diagonally, but there would be none in front where the motor was. (See Fig. 4.) In this first air-ship I had placed the gas escape valves even farther from the motor than I place them to-day. The suspension cords being very long I hung in my basket far below the balloon. Therefore I asked myself: "How could this motor, so far below the balloon, and so far in front of its escape valves, set fire to the gas enclosed in it when such gas is not inflammable until mixed with air?" On this first trial, as in most since, I used hydrogen gas. Undoubtedly when mixed with air it is tremendously inflammable—but it must first mix with air. All my little balloon models are kept filled with hydrogen, and, so filled, I have more than once amused myself by burning inside them, not their hydrogen, but its mixture with the oxygen of the atmosphere. All one has to do is to insert in the balloon model a little