ancient engineers; and the high falsetto of Van Damm occasionally piercing the static from the radio monitor on the bulkhead.
Occasionally too, there were strange variations in the rhythm of our motors and several times I had let the head of the tractor lurch round a little as I struck curious areas of shadow against the rocky wall of the tunnel; Scarsdale's muttered comments were hardly needed but the effect was annoying and made steering more difficult. I glanced in the rear mirror more than once and realised that a malicious corner of my soul was pleased to note that whoever was driving Van Damm's vehicle was not finding things any easier.
And then there came to me in detail the model in Scarsdale's far-off study among the misty hills of Surrey and I found many questions blurting to my tongue. The Professor heard me out in amused silence.
'I was wondering when you would notice,' he said at length. 'The patches of shadow you see are arcades leading to what other caverns and labyrinths God knows. It would take a lifetime to explore them all.'
I was silent for a moment while I absorbed this information.
'You explored some on foot?' I ventured at length.
Scarsdale nodded, his eyes scanning the tunnel ahead.
'I reeled off twine and took a torch but it was hopeless. They were terrifying places. I had a thousand yards of twine and gave up when that ran out. One could wander for years out there, if the hundreds of side tunnels I came across were as extensive.'
I found the implications of the Professor's remarks difficult to take in.
'Then this may be considered a city, with the tunnel its main artery,' I said.
Scarsdale nodded. 'Excellent, Plowright,' he said. 'I had come to much the same conclusion myself.'
He turned to face me in the bluish gloom of the control chamber.
'We have not, of course, had an opportunity thus far to make detailed observations on foot, but there were curious symbols placed at intersections and cross-over points in the tunnels. These, which were strangely incised and high upon the walls, combined with the lack of any observable arrangements for lighting the tunnels — such as torches or brazier fires — led me to believe that the former inhabitants of this place were blind and crept about the passages by feel.'
The Professor's words and the circumstances under which they were uttered had such unpleasant connotations that I fear Number 1 vehicle gave a great lurch which, however, I had started to correct before the Professor's admonition. Such a supposition had not occurred to me and gave rise to such a vivid range of images that I later came to regret the Professor's uncalled-for confidence. I was even, in rather a cowardly fashion, glad that Van Damm's vehicle was to lead the following day, when we hoped to be approaching the underground lake of which Scarsdale had spoken.
We had not planned a very long run that afternoon as we wished to make rather more elaborate arrangements for camping that night. We could not, of course, have fires, even if there had been any driftwood and there was no point in being 'outside' the tractors, when we had their security for sleeping arrangements. I had saved a sandwich from the lunch-break, as I had eaten little due to the excitement engendered by our surroundings, and I juggled the controls precariously as I munched at the tinned ham, occasionally fortifying myself from the thermos-flask of hot tea with which we always provided ourselves each morning at breakfast.
The Professor, when he was not studying the tunnel ahead, was busy on the chart-table with some of his more cryptic books and documents. I noticed once again his typed copy of the ancient and blasphemous Ethics of Ygor and the highly abstruse calculations which Van Damm had referred to as the Trone-Tables. His use of these ciphers and the other media with which the chart-table was strewn were far beyond my knowledge of such things but possibly the Professor had chosen me as his companion in the tractor precisely because I had the layman's mind and he could occasionally put his thoughts into words and test my sometimes banal reactions. With Van Damm he would, more often as not, have engaged in verbal battle in which these two highly trained minds were fairly evenly matched.
Now he sat with his leather-padded sleeves firmly resting on the table, his great shoulders hunched as he studied the figures before him, occasionally shaking as though exasperated beyond measure. Finally, he put his pencil from him and sat up in his chair, swivelling it to face me.
‘I think we might as well call it a day, Plowright,' he said. 'You must find this tiring, and after all, you have done most of the donkey work so far.'
I cast a quick look at the mileage indicator; I shook my head wonderingly as I saw that the day's total — even allowing for our snail's progress this afternoon — registered no less than seventy-one miles. I mentally calculated that the longest street in the world — reputedly in Russia — could have been put down in our tunnel nine or ten times over before it would make an equivalent distance. I simply could not imagine the sophisticated engineering and equipment which would be needed to create such artefacts in the dawn of time and I put further banal self-questioning from me, as Scarsdale spoke again.
'Please give the signal.'
The electric klaxon on top of the tractor blared with heart- stopping raucousness within the tunnel as I pressed the button; Scarsdale would insist on its use as the halt signal either on the surface or under the earth and I myself felt it was something we could do without as the radio link would have been just as effective. But it was Scarsdale's expedition and he made the procedure a rule so we said nothing. Holden's voice came over the radio monitor a few seconds later.
'Executive signal received. What are your instructions?'
'We shall be camping for the night in five minutes,'
Scarsdale replied. 'Please make all necessary preparations.'
The black walls of the tunnel, with an occasional mouth debouching from it, continued to slide by in the yellow glare of our searchlights; already, it seemed as though we had been travelling due north for days. Scarsdale smiled wryly as I observed to him that the Expedition's title was perhaps a little more apposite than hitherto. The warm wind blew as strongly as ever, though fortunately it was still nothing more than a breeze; the air was dry; and the rock grated beneath the rustling tread of the tractors.
Scarsdale was already moving about the cabin, tripping switches which set generators re-charging batteries; testing circuits; and doing the other mundane things on which our survival depended, such as checking levels in the fresh-water tanks and preparing materials for the evening meal, which we would take some time after six o'clock.
I throttled back the motors, my forearms trembling slightly as they were wont to do, after some time spent at the levers, my legs aching from the transmission of the tread movements to the accelerator pedals. Sophisticated as these great machines were, and as cunningly as Scarsdale and Van Damm had designed the transmission mechanisms, they were undoubtedly tiring to drive though the going in these tunnels (I persisted in referring to the broad highways along which we were travelling in the plural) was nowhere as difficult as it had been across the desert.
But there we had the sweet sky above us, and not this lunar blackness which seemed to depress one's spirits beyond measure, even though we had been travelling under the mountains for less than a day; and to recall we had thought the desert sky cruel! I jerked out of my reverie at a sudden exclamation from Scarsdale. He was standing in a stiff attitude in front of the windscreen, his actions arrested in process of tripping one of the switches. The incident was so unusual for him that I might have been more startled than I seemed but I had already begun the stopping procedure of the tractor, so I merely continued with my routine.
The treads rotated ever slower and the shrill whine died away to a minuscule ticking; I switched off then and became aware of the faint respiration of the warm breeze which set up a soft susurrance as of distant surf within the tunnel.
The motor of Van Damm's machine impinged itself upon my consciousness and I turned to see Number 2 stopping behind us; the searchlight on the roof blossomed brighter and several secondary lights came on. By this time I had joined Scarsdale at the windscreen.
'Is there anything wrong?' I asked.
Scarsdale relaxed his tense attitude. He turned towards me and concluded his switching movements on the panel.
'I don't know, Plowright,' he said slowly, his face stern in the yellow atmosphere of the searchlights. 'I fancied I saw something white flicker up ahead in the tunnel.'
