"Better strike another match," said Walt.
"Yes; here goes," agreed Jack. Both boys shouted, to make themselves heard above the now thunderous roaring of the strange noise.
A shout of surprise that rose even above the mysterious roaring, followed the striking of the match. Beyond the turn the path took a steep drop downward, and beyond that—the boys could hardly believe their eyes as they gazed—was the glint of rushing water.
"The subterranean river!" was the amazed cry that broke from the lips of all three.
CHAPTER X.
A NEW MEXICAN STYX.
"The subterranean river!"
The words echoed back weirdly from the vault-like chamber into which they had now penetrated, and at the bottom of which the stream, upon which the light of the match had glistened, flowed rapidly. Within this spacious place the noise was not nearly so loud as it had been when confined in the narrow tunnel, which, in fact, acted much as a speaking-tube would have done.
"It can't be!" gasped Ralph, unwilling to believe his own eyes.