he had maintained when we were training in Surrey.
'Fancies, perhaps,' I said. 'I am possibly over-imaginative where such places as this are involved. Your models, the caves and the other details you gave us in the original briefing were among my major reasons for coming along. Imagination's my strong suit, as you may well know and I certainly need it for my photography and artistic work.'
'And you felt the Great Northern Expedition would give you such scope in your capacity as cinematographer and official cameraman?' he concluded for me.
'Something like that,' I admitted.
The Professor was silent for a long moment and then I heard the soft click as he put the dashboard panel lights on; their blue dimness outlined the details of the cabin.
'But you now feel that your imagination may be a handicap once we get underground?' he continued.
'It may be,' I said. 'Though we shall be within the tractors most of the time. I have been underground before, of course, but it's not just that. There's something different about this trip and not only from what you've said, though that was bizarre enough.'
'Would you care to give me a concrete example?' he asked.
I hesitated for another long moment. Then I told him about my feeling at the entrance of the cave.
'Ah, then you heard it too,' he said sharply. 'I wondered at the time. Yes, it was very like the beating of wings, as you say. Bats, perhaps.'
We did not return to the matter again and in a few moments more we slept. But within I did not think the noise I had heard had been made by bats and I could swear that the Professor did not think so either.
Nine
The honour of being the first one within the great portal was given to Holden; I say honour, such as it was, because the event, like most long-awaited incidents, was almost an anticlimax. We were awake and out early next morning and soon after six a.m. the three tractors affronted the morning air with their motors. What little sun there was penetrated our dank spit of dark sand reluctantly and its gilt was soon lost again against the black, basaltic rock which seemed to absorb light and somehow stain it. The simile is fanciful, I know, but the only one that readily springs to mind.
Holden drove the tractor across past the obelisk and into the cave-mouth where the machine was rapidly lost to sight; Scarsdale was already alongside the entrance and followed him in on foot. We waited for perhaps ten minutes and then both men appeared; Holden re-joined Van Damm in Number 2 tractor and Scarsdale assumed command of Number 1. He put the key of Number 3 vehicle into a drawer in the chart-table; we would pick up the spare vehicle on the way back.
I looked out through the windscreen; Van Damm's machine was describing a circle, ready to fall in behind us and the tinny static of the radio receiver in our cabin was already alive with the doctor's waspish injuctions.
'I will take over the controls, Plowright, if you please,' said Scarsdale. 'I know the route, as you realise and I shall need you to control the radio and searchlights. We shall carry out the same routine we have regularly practised.'
As he spoke I was already vacating my padded chair at the chart-table; to be perfectly candid, I welcomed the arrangement because the radio and other work was nominal, whereas the control of the tractor was exacting, both physically and mentally and likely to be difficult within the winding caverns of which Scarsdale had so often spoken. Besides, I hoped to do some photographic work with the special fast film I had brought along, if Scarsdale's lighting units permitted.
I acknowledged Van Damm's perfunctory verbal message and thanked him for the formal good wishes to Scarsdale for the success of the enterprise. Scarsdale could, of course, hear perfectly well what was being said via the monitor speaker mounted on the bulkhead over the chart-table and he gave an irascible snort at what he considered to be Van Damm's excessive formality. I left the switch at the open position, for that was the instruction, and I should also have to relay back to Van Damm any special orders relating to obstacles we might meet en route.
I ran my eyes over the lighting switchboard and then looked ahead as the massive portal of the huge doorway loomed in front, the lintel lost to sight high above. In the steel rear mirror I could see Van Damm's machine, pennants fluttering, skirting the obelisk; then we were within the cave- mouth and the darkness reached out to embrace us like a cloak. A warm wind blew from the interior of the earth — we had the air vents open and I could feel this — and the whine of the motors echoed back shrilly within the cave walls.
The noise died as Scarsdale reached forward and cut off the air vents from the outside; at the same moment the light of the sky faded to a feeble yellow. At a nod from Scarsdale I switched on the main searchlight, which was mounted in a nacelle above the tractor windscreen and could be swivelled by a control from within the machine. The yellow incandescence, with which we were all to become so familiar, outlined the faint contours of a rocky wall which was lost as it curved upwards into a blackness darker than any night known to outer earth. Shadows fled fantastically across the middle distance and I was momentarily startled to see a vast fluttering until I realised it was our own image thrown upon the tunnel by the searchlight of Van Damm's vehicle behind. I looked briefly in the mirror to see that he had taken station about thirty feet back and acknowledged his movement by using my microphone.
Holden replied laconically; I concentrated ahead and saw that Scarsdale was following the tracks of Number 3 tractor. We saw it a moment or two later, parked up against the right- hand side of the tunnel wall, where it bulged out to make a natural bay. We did not stop but drove straight on, only virgin sand before us now. The tunnel was about thirty feet wide here and it was not to vary much for the next few hours; I had already switched on our measuring instrument so that we could keep a constant check on the miles we covered each day.
I reached for my camera and as Scarsdale grimly concentrated on his steering, I briefly put on all the lighting equipment we possessed; the effect was startling and I busied myself in taking several photographs, both front and rear, before switching down again to the main searchlight only. I had noticed something however, that raised a number of startling conjectures in my mind. Firstly, the roof did not, as is usual in cave formations, come down fairly close to the ground at any point.
The second detail which struck me was that the corridor of stone stretched monotonously ahead for perhaps half a mile and did not vary greatly in its width. The floor also was no longer composed of sand but seemed to be made of rock. This heightened the noise levels within the tunnel considerably, though it made little difference to the comfort and stability of our ride within the tractor. The thing which impressed me most of all, however, was the regularity of the cave walls; before an hour had gone by I had become convinced that the tunnel was not a natural formation at all but had been engineered at some distance remote in time. This raised in its turn a number of fascinating conjectures because I had formed the impression that the inscriptions on the obelisk and the portals of the great doorway were of great antiquity. The engineering problems involved in the vast tunnel along which we were now travelling so smoothly and with as much facility as one would in a modern city's underground system, would have been incredibly complex and difficult without modern machinery and tools. There was a stupefying engineering talent at work here greater than that of the Incas and the Mayans and incomparably older, if what Scarsdale had said was true, and an excitement similar to that which must have animated the Professor in his long years of research and study on the project, began also to animate my own mind.
This must have occurred to Van Damm at almost the precise moment because his high fluting voice came through the loudspeaker, asking to speak to Scarsdale. I told him that was impossible for the moment, as the Professor was at the controls. There was a brief lull, broken only by the crackle of the instrument.
'You have noticed, I take it, the regular conformation of the walls of the tunnel, Plowright,' he began.
'The implications had not escaped me, doctor,' I said.
Scarsdale smiled quietly to himself at the controls.
'Would you please ask the Doctor to maintain radio silence except in emergency,' he said. 'There will be time for discussion and examination of the tunnels when we stop for lunch.'
I conveyed the Professor's message to Van Damm in a more diplomatic manner and with that he had to be
