Thus we pursued our nightmare march, on through that valley of horror. Colder grew the atmosphere and colder. Again the thunder boomed out above us, seeming to shake the roof of the tunnel fiercely, as with Titan hands. A sound of falling water, audible for some time, now grew so loud that conversation became difficult. All the insects had disappeared. "We are approaching the River Starn!" roared Sir Lionel. "Note the dip of the passage and the wet walls!" "Note the type of brickwork!" shouted Smith. Largely as a sedative to the feverish excitement which consumed me, I forced myself to study the construction of the tunnel; and I became aware of an astonishing circumstance. Partly the walls were natural, a narrow cavern traversing the bed of rock which upcropped on this portion of the estate, but partly, if my scanty knowledge of archaeology did not betray me, they were _Phoenician!_ "This stretch of passage," came another roar from Sir Lionel, "dates back to Roman days or even earlier! By God! It's almost incredible!" And now Smith and Kennedy, who lid, were up to their knees in a running tide. An icy shower-bath drenched us from above; ahead was a solid wall of falling water. Again, and louder, nearer, boomed and rattled the thunder; its mighty voice was almost lost in the roar of that subterranean cataract. Nayland Smith, using his hands as a megaphone, cried;-- "Failing the evidence that others have passed this way, I should not dare to risk it! But the river is less than forty feet wide at the point below Monkswell; a dozen paces should see us through the worst!" I attempted no reply. I will frankly admit that the prospect appalled me. But, bracing himself up as one does preparatory to a high dive, Smith, nodding to Kennedy to proceed, plunged into the cataract ahead.... CHAPTER XL THE BLACK CHAPEL Of how we achieved that twelve or fifteen yards below the rocky bed of the stream the Powers that lent us strength and fortitude alone hold record. Gasping for breath, drenched, almost reconciled to the end which I thought was come--I found myself standing at the foot of a steep flight of stairs roughly hewn in the living rock. Beside me, the extinguished lamp still grasped in his hand, leant Kennedy, panting wildly and clutching at the uneven wall. Sir Lionel Barton had sunk exhausted upon the bottom step, and Nayland Smith was standing near him, looking up the stairs. From an arched doorway at their head light streamed forth! Immediately behind me, in the dark place where the waters roared, opened a fissure in the rock, and into it poured the miniature cataract; I understood now the phenomenon of minor whirlpools for which the little river above was famous. Such were my impressions of that brief breathing-space; then-- "Have your pistols ready!" cried Smith. "Leave the lamp, Kennedy. It can serve us no further."