content. We drove along the seemingly endless tunnel for several miles; once I went to the rear of the tractor and read off the mileage indicator. Already it registered fifteen. I told Scarsdale and he merely nodded in a satisfied manner; it was obvious that he knew our destination. His confidence at the controls was masterly and it was uncanny to see the way he almost foresaw any slight shift in our direction; the wind continued to blow steadily and warmly, as I regularly noted by opening the vents. Although the compass needle swung quite broadly on the shallow curves we were sometimes encountering, we were steadily heading almost due north. Eventually, if the Professor's scale models in the far-off study in Surrey were accurate, we should be at an enormous distance beneath the earth. There had been no calls from Van Damm's machine during the remainder of the morning, though the radio switches remained open, but I could see that they were keeping pace with us effortlessly; both tractors were doing a steady ten miles an hour and there was little or no dust beneath the treads to obliterate the view. I was keeping the log this morning and I entered all these details at fifteen minute intervals, to Scarsdale's evident satisfaction. I asked if I might take over the tractor and give him a rest but he shook his head.
'After lunch will be time enough,' he said. 'Compared with the desert this is an extremely comfortable morning's drive.'
We exchanged no further words and I packed up my photographic equipment, my mind completely at rest for the first time since we began our field operations. We were going slightly uphill, I indicated in my last log entry of the morning, made just before our first breaK at 12.15 p.m. The mileage indicator, allowing for a pace that varied between five and ten miles an hour, indicated an awesome fifty-five miles beneath the surface of the mountains.
We did not spend much time within the tractors at lunchtime; the two machines were set up side by side and with the main searchlights illuminating the camping area and the tunnel ahead of us. It was a bare, antiseptic atmosphere; the floor, of hard whitish rock was dry and free of insect or any other type of life that we could see. The walls bore the marks of ancient cutting tools of a type I had never seen before; Van Damm and the others were somewhat excitedly conferring with Scarsdale and I wandered at will, taking pictures and thinking of the people who could have built upon this terrifying scale. I had tilted one of the searchlights upwards toward the roof but despite its power I could not find its limits; there was nothing but inky darkness above and no sign of any bat or bird-life. There would have been an awesome silence that I would have found personally hard to bear, had it not been for the warm and steady breeze that blew from somewhere far off down the tunnel. Altogether, it was a strange, and fascinating place in which we found ourselves.
Geoffrey Prescott and Norman Holden both had an air of barely suppressed excitement, a sort of bubbling effervescence just below the surface, that came through even from under the facade of strictly impersonal scientific materialism which they carried about with them. Like the rest of us, they had now donned light overalls and the alloy helmets which Scarsdale had developed and which were meant to guard us against falling rocks.
This headgear, which bore stencilled numbers, from Scarsdale's appropriate One down to my humble Five, also incorporated powerful flashlights which we found extremely useful, as the light in such a position left our hands free to carry tools and equipment. Both Holden and Prescott carried notebooks and jotted down data, conferring among themselves, as they hurried here and there along the tunnel.
'It conforms fairly closely to your sketches and models, Scarsdale,' Van Damm told the Professor as I wandered close to them. 'Are there any places where the tunnel splits up into tributaries?'
'Only just this side of the water,' Scarsdale said shortly. 'We'll have to leave the machines there and take to the boats. * don't, of course, know what formations we shall find on the other shore. It is perhaps fortunate that there aren't many choices; we could spend years exploring blind alleys, otherwise.'
Van Damm cleared his throat. 'I have noted the marker posts of which you spoke. They would appear to correspond to measurements of ten of our miles.'
The Professor smiled, his face enigmatic in the yellow incandescence of the searchlights.
'I had cause to note them on foot,' he said. 'An experience, I can assure you.'
'How long did it take, Professor?' I asked.
Scarsdale turned his great bearded head toward me in the harsh glare of the lamps.
'I calculated afterwards, over a fortnight,' he said sombrely. 'The worst part was the darkness. I had only a couple of electric torches and some candles, and these had to be conserved. In the end I navigated by using my walking stick against the tunnel wall, much as a blind man might do. I calculated I wore nearly a quarter of an inch off the metal ferrule.'
I could not resist a shudder at the Professor's words and I thought again of the fantastic will inside the hard exterior which had kept him going along these miles of sinister corridors when lesser men might well have been reduced to gibbering idiocy by the darkness and the loneliness.
'You had a compass, I take it?' said Van Damm softly, after a long silence.
'Thank God,' said Scarsdale. 'One becomes completely disorientated. It might be thought a simple matter; right-hand wall going in, say; left-hand going out. But right is left and left is right in the darkness, if you see what I mean. North going in and south going out was the only way, allowing for slight deviations where the tunnel curves.'
I walked on down the tunnel, the faint throbbing of the searchlight generators from the tractors coming over the faint sighing of the wind; the black walls stretched on without a fleck of discoloration or a glimmer of any variation to break their monotony. It was an artery of darkness leading to utter stygian blackness; a man on his own could quickly degenerate to madness in a place like this. I felt for one moment that even without lighting one would still be able to discern the blackness of the tunnel walls. That was the impression the place had on one.
I halted abruptly in my perambulations and came quickly back at this point. There came the tapping of a hammer up ahead; Holden was taking a sample of the rock floor. He swore mildly as I joined him; I looked down and saw that the head of the hammer had snapped from its stout wooden handle. Scarsdale smiled grimly.
'You won't have much luck there, Holden,' he said. 'This material's harder than granite.'
'That's what worries me, Professor,' said Geoffrey Prescott. 'How the hell did these people work such material? And, for all that we're talking about thousands of years remote in time, they must have had more sophisticated tools than we've been able to develop.'
'I have my theories about that also,' said Scarsdale cryptically.
I noticed then that he kept his hand near the revolver strapped to his belt. And I noticed also that a light machine- gun on its stand had been brought out from Number 1 Command tractor, presumably by the Professor while we were finishing lunch. Its workmanlike barrel pointed straight down the tunnel ahead of us.
Ten
We were rumbling slowly ahead again in the inky darkness, our speed reduced to a mere crawl, the searchlight probing the monotonous miles before us. I was steering now, while the Professor sat brooding at the chart-table, every once in a while pausing to stare out of the windscreen; he remained fixed in his attitude for perhaps a quarter of an hour on these occasions and I wondered again what calculations were being evolved within that massive cranium.
Scarsdale had told us we would conserve power in the reduction of speed and though we remained in constant radio contact this first day, I myself thought that Scarsdale hoped to alleviate the monotony of the journey; in truth the somewhat boring and fatiguing routine involved in making the long preliminary approach to the object of our search left one inordinately tired and debilitated. But I noted that Scarsdale's concentration did not relax for one moment and I realised also something of the reasons for the change of driver in Number 1 vehicle and the slackening of speed.
The Professor sat in his padded leather seat behind the chart-table and occasionally would interrupt his calculations to pick up the night-glasses which stood at his elbow and scan the tunnel ahead as though by this he would bring our destination nearer. We had been travelling for more than two hours in this way; the warm air blowing steadily through the vents; the whine of the motors making a repetitive fugue in one's ears; the compass needle swinging ever so slightly with the minute variations in the direction of the tunnel, so accurate were these
