The air about them grew marvellously clear and limpid.

The sun blazed down on them with a tenfold intensity of light, but Zaidie was astonished to find that very little heat penetrated the glass walls and roof of the conning-tower.
"What an awful height!" she exclaimed, looking round at him with something like fear in her eyes.

"How high are we, Lenox ?" "You'll find afterwards that the _Astronef_ doesn't take any account of high or low or up or down," he replied, looking at the dial of an aneroid barometer by the side of him.

"Roughly speaking, we're rather over 60,000 feet--say ten miles--from the surface of the Atlantic.
That's why I asked Andrew whether everything was tight.

You see we couldn't breathe the air there is outside there--too thin and cold--and so the _Astronef_ makes her own atmosphere as we go along.