“I fear so.”

All could share his alarm.

They realized their jeopardy only too well.

Fast where she floated, the airship was almost at the mercy of her enemy’s guns, and it made them feel uneasy.

“To see us is impossible from the forts,” said Frank, “but a stray shot may fly this way and hit us.”

“Can’t we reply?” asked Zamora.

“No. Our gun is not a mortar, and in this case is almost useless,” replied the young inventor, sadly.

“Fo’ de lawd! must we stay heah, an’ take all dey sen’?”

“I see no help for it,” Frank answered.

The prospect made all feel decidedly blue, and they soon heard another report and saw a second shell coming.