National Geographic : 1933 Mar
C' THE RESTIVE BALLOON, PARTIALLY INFLATED, TUGS AT ITS MOORINGS The giant bag is filled with hydrogen to the upper belt, attached to which are the handling ropes. Because thehydrogen tends torise inthedomelike top, the bag looks like a magnified mushroom. The bag is not inflated further before the take-off. Not until thestratosphere isreached does thecarrier become a perfect sphere (see diagram, page 355).