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 rarefied 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.

I sat grasping the stopper with both hands, ready to close it again if, in
spite of our intense hope, the lunar atmosphere should after all prove too
rarefied for us, and Cavor sat with a cylinder of compressed oxygen at
hand to restore our pressure. We looked at one another in silence, and
then at the fantastic vegetation that swayed and grew visibly and
noiselessly without. And ever that shrill piping continued.

My blood-vessels began to throb in my ears, and the sound of Cavor's
movements diminished. I noted how still everything had become, because of
the thinning of the air.

As our air sizzled out from the screw the moisture of it condensed in
little puffs.

Presently I experienced a peculiar shortness of breath that lasted indeed
during the whole of the time of our exposure to the moon's exterior
atmosphere, and a rather unpleasant sensation about the ears and
finger-nails and the back of the throat grew upon my attention, and
presently passed off again.

But then came vertigo and nausea that abruptly changed the quality of my
courage. I gave the lid of the manhole half a turn and made a hasty
explanation to Cavor; but now he was the more sanguine. He answered me in
a voice that seemed extraordinarily small and remote, because of the
thinness of the air that carried the sound. He recommended a nip of
brandy, and set me the example, and presently I felt better. I turned the
manhole stopper back again. The throbbing in my ears grew louder, and then
I remarked that the piping note of the outrush had ceased. For a time I
could not b