Suddenly something struck the metal framework by Nat’s head with a sharp ping!
It was an arrow, and so close had it come to the lad that he had caught its whistling sound as it sped past his ear.
“Phew! This is warm work, with a vengeance,” he muttered.
He saw the Indians give a sudden concerted onrush, yelling like maniacs.
“Keep the searchlight in their eyes. It dazzles them!” called the professor.
Then came another command.
“Let go your ropes!”
Nat and Joe instantly dropped their ropes and seized up rifles.
“Don’t fire!” cried the professor sharply. “We don’t want to injure them if we can help it.”
The great dirigible swayed for an instant and then began to rise.