After another half-hour Smith began to feel the strain of remaining in one position, with all his faculties concentrated.  The air was so calm, and the wind-screen so effective, that he suffered none of the numbing effects which the great speed might otherwise have induced; but it was no light task to keep his attention fixed at once on the engine, the map outspread before him, the compass, and the country below; and by the time he reached a still broader river, which could only be the Rhine, he was tired.  As yet he had been flying for only three hours:  could he live through seven days of it?  He had once crossed America in the Canadian Pacific, and though he got eight hours’ sleep every night, he felt an utter wreck at the end of the journey.  To be sure, he was now in the fresh air instead of a stuffy railway carriage, and he was riding as smoothly as on a steamer, without the jar and jolt that made journeys by rail so fatiguing.  Still, he thought it only good policy to pay heed to the first signs of strain, and so he slowed down until the noise of the engine had abated sufficiently for him to make his voice heard, and said: 

“Roddy, you must take a turn.  We’re near the frontier between Baden and Alsace, I fancy.  The Bavarian hills can’t be far off.  You had better rise a bit, and don’t go too fast, or we may be knocking our noses before we know where we are.”

“Right O, mister,” replied the Frenchman.  “You take forty winks, and eat some chocolate for what you call a nightcap.”

“A good idea.  I’d rise to about 4,500 feet, I think.  Keep your eye on the aneroid.”

They exchanged places.  Smith ate two or three sticks of chocolate, took a good drink of water, and in five minutes was fast asleep.  But his nap lasted no more than a couple of hours.  It appeared to him that he never lost consciousness of his errand.  When he opened his eyes the dawn was already stealing over the sky, and at the tremendous pace to which Rodier had put the engine the aeroplane seemed to rush into the sunlight.  Far below, the earth was spread out like a patchwork, greens and whites and browns set in picturesque haphazard patterns; men moving like ants, and horses like locusts.

“Where are we?” he bawled in Rodier’s ear.

The Frenchman put his finger on the map.  Smith glanced at his watch; it was past five o’clock.  They must be near the Servian frontier.  That broad streak of blue must be the Danube.  Another three hours should see them at Constantinople, the first stage of their journey.  On they rushed, feeling chill in the morning air at the height of nearly five thousand feet.  Lifting his binocular, Smith saw a railway train running in the same direction as themselves, and though from the line of smoke it was going at full speed, it appeared to be crawling like a worm, and was soon left far behind.  Now they were in Bulgaria:  those grey crinkly masses beyond must be the Balkans.  Crossing the Dragoman Pass, they came into an upward current of air that set the machine rocking, and Smith for the first time felt a touch of nervousness lest it should break down and fall among these inhospitable crags.  Rodier planed downwards, until they seemed to skim the crests.  The air was calmer here:  the aeroplane steadied; and when the mountains were left behind they came still lower, following the railway line.