searchlights, in addition to their vibratory communication apparatus and other devices that were explained to Larry.
When he had mastered their operation, which was rendered simple by reason of the fact that they were so nearly automatic, the trio stepped into a lock on the floor of the ship and Professor Stevens ordered them to couple their suits to air-valve connections on the wall, at the same time admitting water by opening another valve.
Swiftly the lock flooded, while their suits inflated.
“All right?” came his vibratory query.
“Right!” they both answered.
“Then stand by for the heavy pressure.”
Wider now he opened the water-valve, letting the ocean in, while at the same time their suits continued inflating through their air-valve connections.
To his surprise, Larry found himself no more inconvenienced by the pressure than he had been from the moment the submarine dove to its present depth. Indeed, most of the air that was coming into his suit was filling the reinforced space between its inner and outer layers, much as the Nereid held air under pressure between her two thick shells.
“All right now?” called out the professor’s vibrator.
“Right!” they called back again.
“Then uncouple your air-valve connections and make ready.”
They did so; and he likewise.
Then, advancing to a massive door like that of a vault, he flung back its powerful clamps, dragged it open – and there beyond, its pressure equaled by that within the lock, loomed the black tide of the ocean bottom.
Awed by this solemn sight, tingling with a sense of unparalleled adventure, Larry stood there a moment, peering out over the threshold of that untrodden world.
Then he followed Diane and her father into its beckoning mystery…
Their searchlights cutting bright segments into the dark, they proceeded toward the vast mound that towered ahead, pushing through a weird realm of phosphorescent fish and other marine creatures.
As they neared it, any possible doubt that it was in fact a pyramid vanished. Corroded by the action of salt water and covered with the incrustations of centuries, it nevertheless presented unmistakable evidence of human construction, rising in steps of massive masonry to a summit shadowy in the murk above.
As Larry stood gazing upon that mighty proof that this submerged plateau had once stood forth proudly above the sea, he realized that he was a party to one of the most profound discoveries of the ages. What a furore this would make when he reported it back to his New York paper!
But New York seemed remote indeed, now. Would they ever get back? What if anything went wrong with their pressure-suits – or if they should become lost?
He glanced back uneasily, but there gleamed the reassuring lights of the Nereid, not a quarter of a mile away.
Diane and her father were now rounding a corner of the pyramid and he followed them, his momentary twinge of anxiety gone.
For some moments, Professor Stevens prowled about without comment, examining the huge basal blocks of the structure and glancing up its sloping sides.
“You see, I was right!” he declared at length. “This is not only a man-made edifice but a true pyramid, embodying the same architectural principles as the Mayan and Egyptian forms. We see before us the visible evidence of a sunken empire – the missing link between Atlantis and America.”
No comments greeted this profound announcement and the professor continued:
“This structure appears to be similar in dimensions with that of the pyramid of Xochicalco, in Mexico, which in turn approximates that of the “Sacred Hill” of Atlantis, mentioned by Plato, and which was the prototype of both the Egyptian and Mayan forms. It was here the Antillians, as the Atlanteans had taught them to do, worshipped their grim gods and performed the human sacrifices they thought necessary to appease them. And it was here, too, if I am not mistaken, that – ”
Suddenly his vibratory discourse was broken into by a sharp signal from the submarine:
“Pardon interruption! Hurry back! We are attacked!”
At this, the trio stood rigid.
“Captain Petersen! Captain Petersen!” Larry heard the professor call. “Speak up! Give details! What has happened?”
But an ominous silence greeted the query.
Another moment they stood there, thoroughly dismayed now. Then came the professor’s swift command:
“Follow me – quickly!”
He was already in motion, retracing his steps as fast as his bulky suit would permit. But as he rounded the corner of the pyramid, they saw him pause, stand staring. And as they drew up, they in turn paused; stood staring, too.
With sinking hearts, they saw that the Nereid was gone.
Stunned by this disaster, they stood facing one another – three lone human beings, on the bottom of the Atlantic ocean, their sole means of salvation gone.
Professor Stevens was the first to speak.
“This is unbelievable!” he said. “I cannot credit it. We must have lost our senses.”
“Or our bearings!” added Diane, more hopefully. “Suppose we look around the other side.”
As for Larry, a darker suspicion flashed through his mind. Captain Petersen! Had he seized his opportunity and led the crew to mutiny, in the hope of converting the expedition into a treasure hunt? Was that the reason he had been so willing to remain behind?
He kept his suspicion to himself, however, and accompanied Diane and her father on a complete circuit of the pyramid; but, as he feared, there was no sign of the Nereid anywhere. The craft had vanished as completely as though the ocean floor had opened and swallowed her up.
But no, not as completely as that! For presently the professor, who had proceeded to the site where they left the craft resting on the sand, called out excitedly:
“Here – come here! There are tracks! Captain Petersen was right! They were attacked!”
Hurrying to the scene, they saw before them the plain evidences of a struggle. The ocean bottom was scuffed and stamped, as though by many feet, and a clear trail showed where the craft had finally been dragged away.
Obviously there was but one thing to do and they did it. After a brief conference, they turned and followed the trail.
It led off over the plateau a quarter mile or more, in an eastward direction, terminating at length beside one of the smaller pyramids – and there lay the Nereid, apparently unharmed.
But her lights were out and there came no answer to their repeated calls, so they judged she must be empty.
What had happened to Captain Petersen and his crew? What strange sub-sea enemy had overcome them? What was now their fate?
Unanswerable question! But one thing was certain. Larry had misjudged the captain in suspecting him of mutiny. He was sorry for this and resolved he would make amends by doing all in his power to rescue him and his men, if they were still living.
Meanwhile his own plight, and that of Diane and her father, was critical. What was to be done?
Suddenly, as all three stood there debating that question, Professor Stevens uttered an exclamation and strode toward the pyramid. Following him with their eyes, they saw him pass through an aperture where a huge block of stone had been displaced – and disappear within.
The next moment they had joined him, to find themselves in a small flooded chamber at whose far end a narrow gallery sloped upward at a sharp angle.
The floor and walls were tiled, they noted, and showed none of the corrosion of the exterior surfaces. Indeed, so immaculate was the room that it might have been occupied but yesterday.
As they stood gazing around in wonder, scarcely daring