As soon as they had hung the ibex-meat upon the curing strings, and pegged out the two skins for drying, they turned their attention to the making of the rope by which they were to be pulled out of their prison. By good fortune they had a large stock of hemp on hand all ready for twisting. It was a store that had been saved up by Ossaroo—at the time when he had fabricated his fish-net; and as it had been kept in a little dry grotto of the cliff, it was still in excellent preservation. They had also on hand a very long rope, though, unfortunately, not long enough for their present purpose. It was the same which they had used in projecting their tree-bridge across the crevasse; and which they had long ago unrove from its pulleys, and brought home to the hut. This rope was the exact thickness they would require: for anything of a more slender gauge would scarcely be sufficient to support the weight of a man’s body; and considering the fearful risk they would have to run, while hanging by it against the face of such a cliff, it was necessary to keep on the safe side as regarded the strength of the rope. They could have made it of ample thickness and strength, so as to secure against the accident of its breaking. But then, on the opposite hand, arose the difficulty as to the strength of the eagle’s wing. Should the rope prove too heavy for the bearcoot to carry over the top of the cliff, then all their labour would be in vain.

“Why not ascertain this fact before making the rope?”

This was a suggestion of Karl himself.

“But how are we to do it?” was the rejoinder of Caspar.

“I think we can manage the matter,” said the botanist, apparently busying his brain with some profound calculation.

“I can’t think of a way myself,” replied Caspar, looking inquiringly at his brother.

“I fancy I can,” said Karl. “What is to hinder us to ascertain the weight of the rope before making it, and also decide as to whether the bird can carry so much?”

“But how are you to weigh the rope until it is made? You know it’s the trouble of making it we wish to avoid—that is, should it prove useless afterwards.”

“Oh! as for that,” rejoined Karl, “it is not necessary to have it finished to find out what weight it would be. We know pretty near the length that will be needed, and by weighing a piece of that already in our hands, we can calculate for any given length.”

“You forget, brother Karl, that we have no means of weighing, even the smallest piece. We have neither beam, scales, nor weights.”

“Pooh!” replied Karl, with that tone of confidence imparted by superior knowledge. “There’s no difficulty in obtaining all these. Any piece of straight stick becomes a beam, when properly balanced; and as for scales, they can be had as readily as a beam.”

“But the weights?” interrupted Caspar. “What about them? Your beam and scales would be useless, I apprehend, without proper weights? I think we should be ‘stumped’ for the want of the pounds and ounces.”

“I am surprised, Caspar, you should be so unreflecting, and allow your ingenuity to be so easily discouraged and thwarted. I believe I could make a set of weights under any circumstances in which you might place me—giving me only the raw material, such as a piece of timber and plenty of stones.”

“But how, brother? Pray, tell us!”

“Why, in the first place, I know the weight of my own body.”

“Granted. But that is only one weight; how are you to get the denominations—the pounds and ounces?”

“On the beam I should construct I would balance my body against a lot of stones. I should then divide the stones into two lots, and balance these against one another. I should thus get the half weight of my body—a known quantity, you will recollect. By again equally dividing one of the lots I should find a standard of smaller dimensions; and so on, till I had got a weight as small as might be needed. By this process I can find a pound, an ounce, or any amount required.”

“Very true, brother,” replied Caspar, “and very ingenious of you. No doubt your plan would do—but for one little circumstance, which you seem to have overlooked.”

“What is that?”

“Are your data quite correct?” naïvely inquired Caspar.

“My data!”

“Yes—the original standard from which you propose to start, and on which you would base your calculations. I mean the weight of your body. Do you know that?”

“Certainly,” said Karl; “I am just 140 pounds weight—to an ounce.”

“Ah, brother,” replied Caspar, with a shake of the head, expressive of doubt, “you were 140 pounds in London—I know that myself—and so was I nearly as much; but you forget that the fret and worry of this miserable existence has reduced both of us. Indeed, dear brother, I can see that you are much thinner since we set out from Calcutta; and no doubt you can perceive the like change in me. Is it not so?”

Karl was forced to give an affirmative reply to the question, at the same time that he acknowledged the ............