through these vines and get at the base of the obelisk,” spoke up the professor, pushing his way forward.
A few minutes later all five stood at the foot of the immense shaft, panting and sweating from their exertions.
As they tore the vines aside, they saw it was covered, at regular intervals, with square bits of stone, exactly like the one found by Prof. Easy.
“Ah!” exclaimed the learned man, as he saw this; “this cube I found evidently came from here. Let us see if we can find where it belongs.”
Leo and Dick quickly produced their knives and began cutting away the vines, while the professor put on his glasses, preparatory to making the examination.
They cleared away all around the base, which was about eighteen feet square, and just as they finished, Dick’s eye lit upon one of the places where a cube was missing.
“Here is the spot,” said he. “Now, professor, let’s see if the one you have fits here.”
The professor stepped forward and produced the cube from his pocket.
He was just about to place it in the opening when a rifle shot rang out close at hand, followed by the baying of a dog.
This so startled the man of science that he made an involuntary move forward, thrusting the cube, as he did so, squarely into the hole.
Almost instantly a hidden door flew noiselessly open, revealing a flight of stone steps, leading downward into the bowels of the earth.
A simultaneous cry of surprise left the lips of the swamp explorers as this remarkable occurrence took place.
They gazed into the opening for the space of a minute and no one spoke a word.
But suddenly they were called to their senses by hearing a wild cry at their very elbow.
The next moment a man and a dog rushed through their midst and sprang down the stairway in the base of the obelisk.
CHAPTER IV.
WHERE THE STAIRS LED TO.
Leo Malvern caught but a fleeting glance at the man and dog as they rushed down the stairs in the base of the obelisk.
But what was the stranger fleeing from?
The swamp explorers glanced around them to find out.
The next moment they learned to their full satisfaction.
In the little clearing, a few yards beyond them, a balloon suddenly settled.
There was but one occupant of the basket, or car, and he was a stern-visaged man of perhaps forty-two.
It was evident that he had not yet seen our friends, for, as the balloon, which was now about half collapsed, settled upon the earth, he sprang from the basket and rushed in the direction taken by the man and dog.
A sudden thought came in Dick Vincey’s head.
“Hide—quick!” he whispered to his companions. “He will most likely enter the opening and go on down.”
In the twinkling of an eye all hands sprang to the other side of the obelisk and concealed themselves in a thicket.
They were not a moment too soon. The next instant the man who had so strangely landed in that wild spot rushed up to the base of the obelisk and came to an abrupt halt.
An exclamation of surprise left his lips as he beheld the opening in the stone shaft.
“By heavens!” he exclaimed, loud enough for the swamp explorers to hear; “Reginald Lacy, you shall not escape me, even if I have to follow you into the very center of the earth!”
Then he boldly entered the doorway and began descending the stone steps.
Five minutes later our friends made their way to the entrance again and listened for some sound.
But they could hear nothing.
“I am going to make a suggestion,” suddenly said Leo.
“What is it?” asked his cousin.
“Let us go down the steps and see what has become of those who have already gone down.”
“Agreed!” exclaimed the professor, who was ready for anything.
“Oh! for de good Lor’ sakes! don’t go down dere. De debbil am dere, suah!” whined Lucky, in a frightened manner.
“Keep still, coon, and don’t git skeered. We may as well go as far and see as much as we kin, since we have got ter this dod-rotted country. I, for one, are satisfied to go down them steps.”
The Yankee gave a contemptuous glance at the darky as he spoke, and then nodded for Leo to lead on.
Dick had not passed his opinion on the question yet, but that he was perfectly willing need scarcely be said.
But at the same time it occurred to him that they ought to take some sort of a light with them.
They had left their supplies at the point where they had been compelled to use the ax in the thicket.
Dick hastened to the spot and got a small lantern, which was all that was left of three that they had brought along with them.
When he reached the obelisk again his companions had already entered the doorway, and were waiting for him on the steps.
It was but the work of a moment to strike a match and light the lantern; and then the boy followed them down into the place beyond.
Down they went, for at least a hundred steps, and the end of the flight was not reached yet.
Another hundred, and still it appeared the same.
“I wonder how many miles we have got ter go afore we git ter ther bottom?” said the Yankee.
“Have patience, Martin,” replied Prof. Easy. “We are on the eve of a great discovery—mark my word for it!”
“Humph! I heerd ye say that same thing a good many times before. But, by the great boots in ther haymow, I stepped on somethin’ alive jist then!”
“A ground hog!” exclaimed Dick, holding up the lantern. “How in thunder did it ever get there, I wonder?”
“If it can live in here, I am sure we can a little longer. Let us proceed,” returned the professor, quietly.
Once more they began descending the steps.
During all this time they had not heard the least sound from those who had preceded them.
Probably one hundred and fifty steps more were descended, and then they reached a wide passage.
“Come,”
