"Certainly—her shape, and other fittings. Now, let's return to the Zeppelin. It's a huge framework of aluminium, built very light and covered with a material of neutral tint."
"Which holds the necessary gas."
"No, Uncle. Which merely covers the aluminium skeleton. Inside the frame there are twenty or more balloonettes, inflated with gas. Thus if one bursts, or two, or more even, the ship still floats."
"Canny that! Smart!" declared Andrew. "Well, yours? It's a similar framework, I suppose? The same balloonettes? Where does the difference come?"
Joe bent again to his bag and produced a parcel, which he rapidly opened. He drew from the interior a sheet of shining material, which might have been glass but for the fact that it was folded half a dozen times. Placing it on the table, this sheet opened to its full capacity as soon as the weight of his fingers was removed.
"Flexible and elastic, you see, Uncle," said Joe. "And yet not extensible. See—it does not stretch. Transparent, of course—one of its least advantages—but yet one of great value in the construction of an airship."
"What! You don't mean to tell me you build the ship of that? How? What part does it form? I—look here, Joe, you're romancing."
Joe smiled; his deep-sunk eyes took on the clever expression, to which his uncle had become familiar. He placed two long objects on the table, and stood leaning the tips of his strong fingers upon them. He might have been a lecturer, and his uncle a student about to absorb his wisdom. As for the objects he had placed on the table, one was a long piece of the same transparent material, an eighth of an inch thick, perhaps, two inches wide before it was bent, and now bent all the way down its length into a right angle. In fact, composed of iron it would be known simply as "angle iron". The other object was a tube, perhaps half an inch in diameter, two feet in length, and of thinner material. Both were transparent, and exceedingly light in weight, as Andrew assured himself instantly.
"Go on," he said huskily. "What is the stuff? Not talc—that I can tell easily. Not celluloid either—you'd never be such a fool as to build a ship of such a highly inflammable material. That stuff's lighter, also. What is it?"
But Joe was not yet to be persuaded into an answer. He spread the thin transparent sheet out, caught the four corners, and taking a jug of water, poured some of the contents into the centre of the sheet. Not a drop penetrated it. Joe demonstrated the fact quietly and without show of haste. Then he stepped to the window and cast the water out. A moment later he was striking a match.