“Yes; they’ve certainly increased the distance between us somewhat,” assented the Professor, “but they’re not as far away as they were a few minutes ago. I don’t understand it. They seem to gain and then we seem to creep up on them a little. Perhaps this may be due to certain effects of the air currents, but it is decidedly peculiar.” Captain Mortimer made no reply. He sat watching the pursued craft, distinctly outlined in the rays of the flash-light. On and on they rushed at topmost speed through the yielding air, grown raw and chilly. The first streaks of light began to flicker in the east. The pursued now rose to still greater altitudes, until the air became uncomfortably rarified. The Professor manipulated his levers and the pursuers followed. “What are they up to now?” asked Captain Mortimer. “Trying to dodge us?” “Perhaps,” answered the Professor. “It looks more to me as if they were trying to keep out of sight of land as the daylight comes.” “Any chance of our giving out?” “No; we can keep this up for many hours yet.” “And they?” “I don’t know. Judging from the qualities they have shown so far, it’s best to assume they are fully as well equipped as we.” “What are the prospects of overtaking them?” “Not very favorable, I should say,” replied the Professor. “We’ve been going at our topmost ever since we started and yet we haven’t gained upon them. In fact, they’ve gained a trifle on us. You see, they are somewhat larger and probably have more power. As it is, I am astonished we haven’t lost them before now.” “What’s the likelihood of our losing them altogether?” “I can’t say,” replied the Professor, “but our chances against losing them improve every minute as the light comes on. We’ll soon be able to at least keep them in sight for a very great distance. You may shut off the flash-light now.” “There’s nothing you can suggest?” “Nothing,” answered the Professor. “Under existing conditions, there are only two courses open to us.” “And they are?” “Either to keep on as we are doing, or give it up as a bad job.” “Give up!” exclaimed Mortimer in a disgusted tone. “I’m unalterably opposed to that. We started out to follow them, and follow them we will until either this air-ship gives out or we overtake them.” “Or we lose sight of them,” suggested the Professor. “Or we lose sight of them,” assented Mortimer grudgingly; “but I trust you’ll do your best to avoid that.” “You may count upon it that I will,” answered the Professor stoutly. “Besides,” continued Mortimer, “they can’t keep this up forever. They’re making for some point and some time or other they must effect a landing. Then it will become interesting. Hello! what are they up to now?” “They are descending. See! they are increasing the distance between us, too.” “If they descend, it will give me a chance to pot them from above,” suggested the Captain, again taking up the rifle.