"That great silk bag which we call the balloon was filled with coal-gas, and coal-gas is only abouthalf as heavy as air. When the great bag is full of this gas, therefore, it is not only able to rise in the air itself, but it is able also to carry up with it car and men too."SUMMARY
Balloons float in the air, because they are filled with coal- gas, which is only about half as heavy as the air. The dense, heavy air forces the balloon up, just as water forces a cork to its surface.
Lesson 37
How The Fish Moves
