Page:My Airships.djvu/60

 in his basket, Fig. 1, b, the centre of gravity of the whole system is not shifted appreciably. In a very small balloon the centre of gravity, Fig. 2, a, is undisturbed only so long as the aeronaut sits straight in the centre of his basket. When he moves to the right the centre of gravity, Fig. 2, b, is shifted beyond the vertical line of the balloon's circumference, causing the balloon to swing in the same direction. Therefore, they said, your necessary movements in the basket will cause your little balloon to roll and swing continually. "We shall make the suspension tackle longer in proportion," I replied. It was done, and the "Brazil" proved remarkably stable. When I brought my light Japanese silk to M. Lachambre he looked at it and said: "It will be too weak." But when we came to try it with the dynamometer it surprised us. Tested thus, Chinese silk stands over 1000 kilogrammes (or 2200 lbs.) strain to the linear metre (3*3 feet). The thin Japanese silk stood a strain of 700 kilogrammes (1540 lbs.)—that is, it proved to be thirty times stronger than necessary according to the theory of strains. This is astonishing when you consider that it weighs only 30 grammes (a little