I sat down with my legs on either side of the manhole and prepared to unscrew it, but Cavor stopped me. “There is first a little precaution,” he said. He pointed out that although it was certainly an oxygenated atmosphere outside, it might still be so rarified as to cause us grave injury. He reminded me of mountain sickness, and of the bleeding that often afflicts aeronauts who have ascended too swiftly, and he spent some time in the preparation of a sickly-tasting drink which he insisted on my sharing. It made me feel a little numb, but otherwise had no effect on me. Then he permitted me to begin unscrewing.

Presently the glass stopper of the manhole was so far undone that the denser air within our sphere began to escape along the thread of the screw, singing as a kettle sings before it boils. Thereupon he made me desist. It speedily became evident that the pressure outside was very much less than it was within. How much less it was we had no means of telling.