Chapter XIX. The Underground River
 

They gathered around the opening so unexpectedly disclosed to them, and stared down into the black depths. Beyond the first few steps of the flight that led to they knew not where, nothing could be seen. In his impatience Tom was about to go down.

"Bless my match box!" cried Mr. Damon. "What are you going to do, Tom, my boy?"

"Go down there, of course! What else? I want to get to the underground city."

"Don't!" quickly advised the odd man. "You don't know what's there. It may be a trap, where the old Aztecs used to throw their victims. There may be worse things than bats there. You'll need torches-- lights--and you'd better wait until the air clears. It may have been centuries since that place was opened."

"I believe that's right," agreed Ned. "Whew; Smell it! It's as musty as time!"

An unpleasant odor came up the tunnel entrance, and it was stifling to stand too close. Tom lighted a match and threw it down. Almost instantly the flame was snuffed out.

"We couldn't live down there a minute," said the young inventor. "We've got to wait for it to clear. We'll go back to the balloon and get some electric flash lamps. I brought along a lot of 'em, with extra strong batteries. I thought we'd need some if we did find the city of gold, and it looks as if we were almost there now."

Tom's plan was voted good so they hurried out of the temple, their feet echoing and re-echoing over the stone floor. The place, ruined and desolate as it was, had no terrors for them now. In fact they were glad of the very loneliness, and Tom and Ned actually looked about apprehensively as they emerged, fearing they might see a sign of the Mexicans or the Fogers.

"Guess they can't pick up our trail," said Tom, when, he saw of what Ned was thinking.

"No, we've got the place to ourselves. I wonder how long it will take for the air to get fresh?"

"Not so very long, I guess. There was a good draught. There must be some opening in the underground city by which the air is sucked in. They'd never have only one opening to it. But we don't need to look for the other. Come on, we'll get out the torches."

These electrical contrivances are familiar to all boys. A small electric lamp is set in the end of a hollow tube of tin, and about the lamp is a reflector. Dry electrical batteries are put in the tin tube, and by means of a push button the circuit is closed, illuminating the lamp, which gives a brilliant glow. Tom had a special kind of lamp, with tungsten filaments, which gave a very powerful light, and with batteries designed to last a long time. A clip on the spring controlling the push button made it so that the lamp could be made to give a steady glow. Thus they were well prepared for exploring the tunnel.

It took some little time to get the flash lamps ready, and when they were all charged and they had eaten, they went back to the opening to see if the air had cleared. Tom tested it by dropping a match down, and, to his delight it burned with a clear flame.

"It's all right!" he exclaimed. "The air is pure. Now to see where we will bring up. Come on, everybody."

"Jest one minute, Massa Tom," begged Eradicate, as the young inventor was about to descend the steps, which even the brightness of his lamp did not disclose the end. "Is yo' gwine down dar, Massa Tom?"

"Certainly, Rad."

"An' is yo'--'scuse me--but is yo' expectin' me fo' t' follow yo'?"

"Certainly, Rad."

"Den, all I's got t' say is dat yo' is 'spectin' too much. I ain't gwine t' bury mahse'f alive not yit."

"But, Rad, this is where the gold images are. If you don't come down with us you won't get any gold."

"Am dat so? No gold?" The colored man scratched his head. "Well, I shore does want gold," he murmured. "I reckon I'd better trot along. But one thing mo', Massa Tom."

"What is it, Rad?"

"Was yo' all aimin' t' stay down thar any length ob time? 'Case if yo' is yo' all'd better take along a snack ob suffin' t' eat. 'Case when I gits among gold I don't want t' come out very soon, an' we might stay dar all day."

"Good advice, Rad," exclaimed Ned with a laugh. "I think we may get hungry. You go back and put us up a lunch. We'll wait for you."

"Bless my napkin ring! I think you're right!" exclaimed Mr. Damon, and Eradicate hurried back to the balloon to get some of the condensed food.

He was soon back and then, with Tom in the lead, and with everyone carrying an electric torch, with a spare one in reserve, and with their weapons in readiness the party descended the stone steps.

Their footfalls echoed solemnly as they went down--down into the unknown blackness. They kept their bright lights playing here and there, but even these did not dispell the gloom. On every side was stone--stone walls--stone steps. It was like going down into some vast stretch of catacombs.

"Say, will we ever get to the bottom?" asked Ned, when they had counted several hundred steps. "Maybe this goes down to the middle of the earth."

"Well, ef it do I'm gwine right along!" called Eradicate. "I's gwine t' hab one ob dem gold images or bust!"

"And I'm with you!" cried Tom. "We'll have to get to the bottom sooner or later."

Hardly had he spoken than he came to the last step, and saw stretching off before him a long tunnel, straight and level, lined on both sides, and bottom, with smooth stones that gleamed like marble.

"Now we are really in the tunnel," declared Ned. "I wonder what's at the end?"

"The city of gold, of course," answered Tom confidently.

Eagerly they hurried on. There was a slightly musty smell to the air, but it was fresher than might have been expected.

Suddenly Tom, who was in advance, uttered a cry. It sounded like one of alarm, and Ned yelled:

"What's the matter?"

"Look here!" cried Tom. They hurried up to him, to find him standing before a sort of niche in the wall. And the niche was lined with a yellow metal that gleamed like gold, while in it was one of the golden images, the second one they had seen, and the third they heard about.

"We're on the trail! We're on the trail!" cried Tom.

"Heah! Let me hab dat!" cried Eradicate. "I may not git anudder," and he reached up for the statue.

"Let it stay until we come back," suggested Mr. Damon.

"Somebody might take it," said the colored man.

"Who?" laughed Tom. "There's not a soul here but ourselves. But take it, if you want it, Rad," and Eradicate did so, stuffing the image, which was only about four inches high, into his pocket.

Then they went on, and they saw several other images, though not of gold. Several niches were lined with yellow metal, but whether it was gold or not they could not tell. They did not want to stop, as they were anxious to get to the underground city.

"Hark! What's that?" asked Tom, when they had gone about a mile along the tunnel. "Don't you hear something?"

"Sounds like a roaring," agreed Ned. "Maybe it's more of the bats."

"Doesn't sound like bats," declared Tom. "It's more like a waterfall. Come on."

They hurried forward, the strange sound increasing at every step, until it filled the tunnel with its menacing roar.

"That's strange," said Tom in worried tones. "I hope we don't come to a waterfall."

Suddenly the tunnel made a turn, and as they went around the curve in the wall the sound smote on their ears with increased violence. Tom raced forward, focusing his electric lamp down on the stone corridor. The next instant he cried out:

"A river! It's an underground river and we can't go any further! We're blocked!"

The others came to his side, and there, in the glare of their lamps, they saw rushing along, between two walls of stone, a dark stream which caused the roaring sound that had come to them. The tunnel was cut squarely in two by the stream, which was at least thirty feet wide, and how deep they could only guess. Swiftly it flowed on, its roar filling the tunnel.