Directly before me the river ran into this smaller chamber through three separate arched openings.

Thurid and the therns were nowhere to be seen-into which of the dark holes had they disappeared? There was no means by which I might know, and so I chose the center opening as being as likely to lead me in the right direction as another.

Here the way was through utter darkness. The stream was narrow-so narrow that in the blackness I was constantly bumping first one rock wall and then another as the river wound hither and thither along its flinty bed.

Far ahead I presently heard a deep and sullen roar which increased in volume as I advanced, and then broke upon my ears with all the intensity of its mad fury as I swung round a sharp curve into a dimly lighted stretch of water.

Directly before me the river thundered down from above in a mighty waterfall that filled the narrow gorge from side to side, rising far above me several hundred feet-as magnificent a spectacle as I ever had seen.

But the roar-the awful, deafening roar of those tumbling waters penned in the rocky, subterranean vault! Had the fall not entirely blocked my further passage and shown me that I had followed the wrong course I believe that I should have fled anyway before the maddening tumult.

Thurid and the therns could not have come this way. By stumbling upon the wrong course I had lost the trail, and they had gained so much ahead of me that now I might not be able to find them before it was too late, if, in fact, I could find them at all.

It had taken several hours to force my way up to the falls against the strong current, and other hours would be required for the descent, although the pace would be much swifter.

With a sigh I turned the prow of my craft down stream, and with mighty strokes hastened with reckless speed through the dark and tortuous channel until once again I came to the chamber into which flowed the three branches of the river.

Two unexplored channels still remained from which to choose; nor was there any means by which I could judge which was the more likely to lead me to the plotters.

Never in my life, that I can recall, have I suffered such an agony of indecision. So much depended upon a correct choice; so much depended upon haste.

The hours that I had already lost might seal the fate of the incomparable Dejah Thoris were she not already dead-to sacrifice other hours, and maybe days in a fruitless exploration of another blind lead would unquestionably prove fatal.

Several times I essayed the right-hand entrance only to turn back as though warned by some strange intuitive sense that this was not the way. At last, convinced by the oft-recurring phenomenon, I cast my all upon the left-hand archway; yet it was with a lingering doubt that I turned a parting look at the sullen waters which rolled, dark and forbidding, from beneath the grim, low archway on the right.

And as I looked there came bobbing out upon the current from the Stygian darkness of the interior the shell of one of the great, succulent fruits of the sorapus tree.

I could scarce restrain a shout of elation as this silent, insensate messenger floated past me, on toward the Iss and Korus, for it told me that journeying Martians were above me on that very stream.

They had eaten of this marvelous fruit which nature concentrates within the hard shell of the sorapus nut, and having eaten had cast the husk overboard. It could have come from no others than the party I sought.

Quickly I abandoned all thought of the left-hand passage, and a moment later had turned into the right. The stream soon widened, and recurring areas of phosphorescent rock lighted my way.

I made good time, but was convinced that I was nearly a day behind those I was tracking. Neither Woola nor I had eaten since the previous day, but in so far as he was concerned it mattered but little, since practically all the animals of the dead sea bottoms of Mars are able to go for incredible periods without nourishment.

Nor did I suffer. The water of the river was sweet and cold, for it was unpolluted by decaying bodies-like the Iss-and as for food, why the mere thought that I was nearing my beloved princess raised me above every material want.

As I proceeded, the river became narrower and the current swift and turbulent-so swift in fact that it was with difficulty that I forced my craft upward at all. I could not have been making to exceed a hundred yards an hour when, at a bend, I was confronted by a series of rapids through which the river foamed and boiled at a terrific rate.

My heart sank within me. The sorapus nutshell had proved a false prophet, and, after all, my intuition had been correct-it was the left-hand channel that I should have followed.

Had I been a woman I should have wept. At my right was a great, slow-moving eddy that circled far beneath the cliff's overhanging side, and to rest my tired muscles before turning back I let my boat drift into its embrace.

I was almost prostrated by disappointment. It would mean another half-day's loss of time to retrace my way and take the only passage that yet remained unexplored. What hellish fate had led me to select from three possible avenues the two that were wrong?

As the lazy current of the eddy carried me slowly about the periphery of the watery circle my boat twice touched the rocky side of the river in the dark recess beneath the cliff. A third time it struck, gently as it had before, but the contact resulted in a different sound-the sound of wood scraping upon wood.

In an instant I was on the alert, for there could be no wood within that buried river that had not been man brought. Almost coincidentally with my first apprehension of the noise, my hand shot out across the boat's side, and a second later I felt my fingers gripping the gunwale of another craft.

As though turned to stone I sat in tense and rigid silence, straining my eyes into the utter darkness before me in an effort to discover if the boat were occupied.

It was entirely possible that there might be men on board it who were still ignorant of my presence, for the boat was scraping gently against the rocks upon one side, so that the gentle touch of my boat upon the other easily could have gone unnoticed.

Peer as I would I could not penetrate the darkness, and then I listened intently for the sound of breathing near me; but except for the noise of the rapids, the soft scraping of the boats, and the lapping of the water at their sides I could distinguish no sound. As usual, I thought rapidly.

A rope lay coiled in the bottom of my own craft. Very softly I gathered it up, and making one end fast to the bronze ring in the prow I stepped gingerly into the boat beside me. In one hand I grasped the rope, in the other my keen long-sword.

For a full minute, perhaps, I stood motionless after entering the strange craft. It had rocked a trifle beneath my weight, but it had been the scraping of its side against the side of my own boat that had seemed most likely to alarm its occupants, if there were any.

But there was no answering sound, and a moment later I had felt from stem to stern and found the boat deserted.

Groping with my hands along the face of the rocks to which the craft was moored, I discovered a narrow ledge which I knew must be the avenue taken by those who had come before me. That they could be none other than Thurid and his party I was convinced by the size and build of the boat I had found.

Calling to Woola to follow me I stepped out upon the ledge. The great, savage brute, agile as a cat, crept after me.

As he passed through the boat that had been occupied by Thurid and the therns he emitted a single low growl, and when he came beside me upon the ledge and my hand rested upon his neck I felt his short mane bristling with anger. I think he sensed telepathically the recent presence of an enemy, for I had made no effort to impart to him the nature of our quest or the status of those we tracked.