Just then one of the sailors manning the trail ropes kicked the piece of packing. It fell literally into Hamerton's hands.
Hamerton and his comrade exchanged glances of satisfaction. They dared not speak. They realized that they had made a great discovery.
Directly the experimental airship was safely housed the men in attendance were marched off, presumably to breakfast, and the occupants of the machinery pit were able to discuss their find.
"It's cotton waste, right enough," said Hamerton.
"And asbestos fibre," said Detroit, plucking out a piece of core. "I suppose that renders the waste non-inflammable?"
"Hardly," replied the Sub. "Besides, how do you account for the stuff being gas-proof? It's as porous as a sponge."
Detroit put a small quantity of the stuff between his teeth.
"Ugh!" he exclaimed. "There's alum in it, and gum arabic in a viscous state, only this piece has got slightly dry. I guess I see the trick. They pack the space between the outer and inner skins with the stuff under pressure. There is not sufficient resistance to cause the shell to explode, therefore the projectile passes completely through, making only a small aperture that instantly closes behind. They made a severe test, for the Zeppelin was practically a captive balloon. Had she been travelling at from thirty to fifty knots at an uncertain range it would have been a difficult matter to get a shot home."
"Do you know what they were firing with?" asked Hamerton.
"A pom-pom, I should imagine."