I knew, though, that Triton was of the same approximate size as Earth's own moon, and revolved around the great planet at the same approximate distance as Earth's own moon, roughly a quarter of a million miles. As we had noted from our space-flier in flashing out toward Neptune, its moon was now behind the great planet, that is on the other side of it from the sun, but due to the sharp inclination of the plane of Triton's orbit around Neptune, it was so much higher than its great planet in space as to make it possible to see the single moon, even from Neptune's sunward side. And now as our eleven cylinders shot toward it, it was spreading out across the black vault of the heavens before and above us, until at last we were within a few thousand miles of it and the speed of the cylinder was perceptibly decreasing beneath the controls of the three at the central standard.
Smoothly the cylinder, and the ten behind it, slowed, until they were racing forward at a comparatively low velocity. Triton's dull-gleaming sphere filled the heavens before us. Behind and a little below the great green disk of Neptune, belted with the vast cloud-masses of its immense atmosphere, loomed almost as great as ever to our eyes. And far beyond it there burned the sun's bright little disk, just above the huge sphere of Neptune, and visible to us through the thinner vapors of Neptune's uppermost atmosphere. We turned back toward the nearer world of Triton. As the cylinders rushed on toward it, all the suspense of expectation and mystery that had been ours since our first arrival at the strange dead world of Neptune gripped us now with renewed power. And as Marlin and I stared ahead we were aware that the cylinders were dropping, swinging about our pivoted seats and dropping toward the surface of Triton that seemed now to gleam beneath us.
Toward it we smoothly shot, and as Marlin and I gazed intently down we saw that there were below none of the great cloud-masses that wreathed the surface of mighty Neptune. Instead was only a smooth and strangely gleaming surface that we could but vaguely glimpse, and the sight of which made my heart pound in sudden anticipation. Could the thing be—could it be that here upon Triton as upon Neptune——? But my wondering speculations were cut abruptly short by reality as we shot lower toward the surface of Triton, as that surface came clearly at last to the eyes of Marlin and myself, bringing involuntary exclamations of amazement from us. For that surface was metal! Triton was shielded on all sides by a giant metal roof similar to that which enclosed great Neptune itself!
Down toward that mighty roof our eleven cylinders were rushing. When they seemed just above it, they halted their drop and raced along above it, around Triton's vastly curving surface. As they did so, Marlin and I, gazing downward, saw that the vast roof that shielded Triton appeared to be, from above, of the same dark metal as that which protected Neptune, and that it extended away without break or seam as far as we could see over the big moon's surface. And as our cylinders flashed above it, around the world's surface, we were aware that Triton had an atmosphere even as had its great parent-world, since from outside was coming the dull roar of air against the speeding cylinder. It was a fact startling enough, but at that moment it was driven from our minds by a thing more startling still.
For as we flashed thus around Triton's sunward side, Marlin suddenly uttered a hoarse exclamation, pointed ahead and to the left. I gazed in that direction instantly and for a moment saw nothing unusual, but then as the cylinders flashed on I saw that in that direction was what seemed a great round opening in the smooth, dark metal, a titanic circular opening that must be miles across. Up out of that opening was rising what seemed at first glance a vast cylinder of pale light that sprang straight up and outward from the gigantic opening, and that was only visible for a short distance above that opening, fading swiftly into invisibility as it shot out into the gulf of space from Triton. Instinctively my eyes followed the fading length of that mighty beam outward, and then as they did so I felt sudden, awed understanding descending upon me and stared with Marlin toward the giant pit and its great ray in stunned silence. For that giant ray was pointing straight into the great gulf of space, toward the tiny, fiery disk of the distant sun!
"The giant force-ray!" Marlin whispered. "The great force-ray that's turning the sun ever faster—and that we came out here to find!"
"And pointing straight toward the sun!" I exclaimed. "Pointing through Neptune's upper atmosphere toward the sun!"
For we could see now that the giant ray, visible only there at its source, must indeed be cleaving through the upper limits of great Neptune's atmosphere as it reached across the great gulf toward the sun. For since Triton was on the other side of Neptune from the sun, was on its outward side, the great green sphere of Neptune lay almost between the sun and Triton, the big moon being high enough above the great planet, though, due to the inclination of its orbital plane, to make the sun visible to it through the upper reaches of Neptune's vast atmosphere. Through that atmosphere, therefore, we knew, the giant force-ray must be driving on its path across the solar system toward the sun, hurtling across the gulf to strike against that spinning sun's edge with terrific pressure and to spin it ever faster toward that day of division and doom that was marching relentlessly upon it!
But as our cylinders now swept nearer toward the giant force-ray and the pit from which it stabbed up and outward, Marlin and I were staring obliquely down into that vast pit. Seen from the side as we saw it, the tremendous opening seemed only like a mighty well of metal, from which the colossal pale force-ray, almost as great in diameter as the huge pit, stabbed. We could see, however, that set near the great pit's top at regular intervals around its curving wall were what seemed metal cube-like rooms, which were set on the pit's smooth curving wall. They were a score in number, those out-jutting metal cubes, and from slits in their walls came light from within, and glimpses of stud-covered walls and Neptunians moving about them. We knew, without doubt, that those twenty cubes held within them the unthinkably complex controls of this mighty force-ray that was destroying the solar system!