We did not get our impression of that cavern all at once.  Our attention was taken up by the movements and attitudes of the Selenites immediately about us, and by the necessity of controlling our motion, lest we should startle and alarm them and ourselves by some excessive stride.  In front of us was the short, thick-set being who had solved the problem of asking us to get up, moving with gestures that seemed, almost all of them, intelligible to us, inviting us to follow him.  His spout-like face turned from one of us to the other with a quickness that was clearly interrogative.  For a time, I say, we were taken up with these things.

But at last the great place that formed a background to our movements asserted itself.  It became apparent that the source of much, at least, of the tumult of sounds which had filled our ears ever since we had recovered from the stupefaction of the fungus was a vast mass of machinery in active movement, whose flying and whirling parts were visible indistinctly over the heads and between the bodies of the Selenites who walked about us.  And not only did the web of sounds that filled the air proceed from this mechanism, but also the peculiar blue light that irradiated the whole place.  We had taken it as a natural thing that a subterranean cavern should be artificially lit, and even now, though the fact was patent to my eyes, I did not really grasp its import until presently the darkness came.  The meaning and structure of this huge apparatus we saw I cannot explain, because we neither of us learnt what it was for or how it worked.  One after another, big shafts of metal flung out and up from its centre, their heads travelling in what seemed to me to be a parabolic path; each dropped a sort of dangling arm as it rose towards the apex of its flight and plunged down into a vertical cylinder, forcing this down before it.  About it moved the shapes of tenders, little figures that seemed vaguely different from the beings about us.  As each of the three dangling arms of the machine plunged down, there was a clank and then a roaring, and out of the top of the vertical cylinder came pouring this incandescent substance that lit the place, and ran over as milk runs over a boiling pot, and dripped luminously into a tank of light below.  It was a cold blue light, a sort of phosphorescent glow but infinitely brighter, and from the tanks into which it fell it ran in conduits athwart the cavern.

Thud, thud, thud, thud, came the sweeping arms of this unintelligible apparatus, and the light substance hissed and poured.  At first the thing seemed only reasonably large and near to us, and then I saw how exceedingly little the Selenites upon it seemed, and I realised the full immensity of cavern and machine.  I looked from this tremendous affair to the faces of the Selenites with a new respect.  I stopped, and Cavor stopped, and stared at this thunderous engine.

“But this is stupendous!” I said.  “What can it be for?”