It is a bag filled with gas, and used for sailing in the air.
Fig. 19.
What is placed over this bag?
A network of ropes is placed over it, and they are so arranged as to extend beneath the bag, as is represented in [Fig. 19].
What is fastened to these ropes?
A car or basket is fastened to these ropes.
What is the car or basket for?
It is to carry up those who wish to ascend with the balloon.
How large are balloons usually made?