"If you asked me, I'd say we couldn't last another three hours anyway," replied Stanley with a shrug. "These fish have out-thought us!"

"Nonsense! There may still be a way—"

"A brace of machine-guns...." I murmured hopefully.

"You might as well wish for a dozen light cannon!" snapped the Professor. "Please try to concentrate, and see if any effective weapon suggests itself to you—something more available at the moment than machine-guns."

In silence the three of us racked our brains for a means of defence. Aga, leaving for a time the task of soothing her more hysterical subjects, came quietly over to us and sat on the bench beside me.

Frankly I could think of nothing. To my mind we were surely doomed. What arms could possibly be contrived at such short notice? What weapon could be called forth to be effective against the thick glass helmets?

But as I glanced at Stanley I saw his face set in a new expression as his thoughts took a turn that suggested possible salvation.

"Glass," he muttered. "Glass. What destroys it? Sharp blows ... certain acids ... variation in temperature ... heat and cold.... That's it! That's it!"

He turned excitedly to the Queen.

"I think we have it! At least it's worth trying. If there is any tubing around...." He stopped as he realized he was talking in English, and resumed stiltedly in Aga's own language.