"Wait a minute," I called. "I've just thought of something."

I climbed inside the tractor cabin and shook Mahler. Fortunately, he was only asleep – from the look of him an hour or two ago I'd have said the collapse was due any minute.

"Mr Mahler," I said quickly. "You said you worked for an oil company?"

"That's right." He looked at me in surprise. "Socony Mobil Oil Co., in New Jersey."

"As what?" There were a hundred things he could have been that were of no use to me.

"Research chemist. Why?"

I sighed in relief, and explained. When I'd finished telling him of Hillcrest's solution to his troubles – distilling the petrol – I asked him what he thought of it.

"It's as good a way as any of committing suicide," he said grimly. "What does he want to do – send himself into orbit? It only requires one weak spot in the can he's trying to heat.. . . Besides, the evaporation range of petrol is so wide – anything from 30 degrees centigrade to twice the temperature of boiling water -that it may take him all day to get enough to fill a cigarette lighter."

"That seems to be more or less the trouble," I agreed. "Is there nothing he can do?"

"Only one thing he can do – wash it. What size drums does your petrol come in?"

Ten gallon."

"Tell him to pour out a couple of gallons and replace with water. Stir well. Let it stand for ten minutes and then syphon off the top seven gallons. It'll be as near pure petrol as makes no difference."

"As easy as that!" I said incredulously. I thought of Hillcrest's taking half an hour to distil a cupful. "Are you sure, Mr Mahler?"

"It should work," he assured me. Even the strain of a minute's speaking had been too much for him, his voice was already no more than a husky whisper. "Sugar is insoluble in petrol – it just dissolves in the small amounts of water present in petrol, small enough to be held in suspension. But if you've plenty of water it'll sink to the bottom, carrying the sugar with it."

"If I'd the Nobel Science Prize, I'd give it to you right now, Mr Mahler." I rose to my feet. "If you've any more suggestions to make, for heaven's sake let me know."

"I've one to make now," he smiled, but he was almost gasping for breath. "It's going to take your friend a pretty long time to melt the snow to get all the water he needs to wash the petrol." He nodded towards the tractor sled, visible through the gap in the canvas screen. "We're obviously carrying far too much fuel. Why don't you drop some off for Captain Hillcrest-why, in fact, didn't you drop some off last night, when you first heard of this?"

I stared at him for a long long moment, then turned heavily for the door.

"I'll tell you why, Mr Mahler," I said slowly. "It's because I'm the biggest damned prize idiot in this world, that's why."

And I went out to tell Hillcrest just how idiotic I was.

CHAPTER TEN – Thursday 4 P.M. – Friday 6 P.M.

Jackstraw, Corazzini and I took turns at driving the Citroen all through that evening and the following night. The engine was beginning to run rough, the exhaust was developing a peculiar note and it was becoming increasingly difficult to engage second gear. But I couldn't stop, I daren't stop. Speed was life now.

Mahler had gone into collapse shortly after nine o'clock that evening, and from the collapse had gradually moved into the true diabetic coma. I had done all I could, all anyone could, but heaven only knew it was little enough. He needed bed, heat, fluids, stimulants, sugar by mouth or injection. Both suitable stimulants and the heat were completely lacking, the lurching, narrow, hard wooden bunk was poor substitute for any bed, despite his great thirst he had found it increasingly difficult to keep down the melted snow water, and I had no means of giving an intravenous injection. For the others in the cabin it was distressing to watch him, distressing to listen to the dyspnoea – the harsh laboured breathing of coma. Unless we could get the insulin in time, I knew no power on earth could prevent death from supervening in from one to three days – in these unfavourable conditions, a day would be much more likely.

Marie LeGarde, too, was weakening with dangerous speed. It was with increasing difficulty that she could force down even the smallest mouthfuls of food, and spent most of her time in restless troubled sleep. Having seen her on the stage and marvelled at her magnificent vitality, it now seemed strange to me that she should go under so easily. But her vitality had really been a manifestation of a nervous energy: she had little of the physical resources necessary to cope with a situation like this, and I had frequently to remind myself that she was an elderly woman. Not that any such reminder was needed when one saw her face: it was haggard and lined and old.

But worried though I was about my patients, Jackstraw was even more deeply concerned with the weather. The temperature had been steadily rising for many hours now, the moaning ululation of the ice-cap wind, which had been absent for over two days, was increasing in intensity with every hour that passed, and the skies above were dark and heavy with black drifting clouds of snow. And when, just after midnight, the wind-speed passed fifteen miles an hour, the wind began to pick up the drift off the ice-cap.

I knew what Jackstraw was afraid of, though I myself had never experienced it. I had heard of the katabatic winds of Greenland, the equivalent of the feared Alaskan wllliwaws. When great masses of air in the heart of the plateau were cooled, as they had been in the past forty-eight hours, by extremely low temperatures, they were set in motion by a gradient wind and cascaded – there was no other word for it – downwards from the edge of the plateau through suitable drainage channels. Set in motion through their own sheer weight of cold air, these gravity or drainage winds, slowly wanned by the friction and compression of their descent, could reach a hurricane force of destructive violence in which nothing could live.

And all the signs, all the conditions for a gravity storm were there. The recent extreme cold, the -rising wind, the rising temperature, the outward flowing direction of the wind, the dark star-obscuring clouds scudding by overhead – there could be no mistaking it, Jackstraw declared. I had never known him to be wrong about Greenland weather, I didn't believe him to be wrong now, and when Jackstraw became nervous it was time for even the most optimistic to start worrying. And I was worried all right.

We drove the tractor to its limit, and on the slight downward slope – we had changed direction by this time and were heading due south-west for Uplavnik – we were making very good time indeed. But by four o'clock in the morning, when we were, I reckoned, not more than sixty miles from Uplavnik, we ran into the sastrugi and were forced to slow down.

The sastrugi, regular undulations in the frozen snow, were the devil on tractors, especially elderly machines like the Citroen. Caused by raking winds, symmetrical as the waves in an eighteenth-century sailing print, hard on the crest and soft in the trough, they made progress possible only by slowing down to a disheartening crawl. Even so the Citroen and the sledges behind rolled and pitched like ships in a heavy seaway, the headlights one moment reaching up into the lowering darkness of the sky, the next dipping to illuminate the barred white and shadowed black of the sastrugi immediately ahead. Sometimes it gave way to deceptively clear patches – deceptively, for snow had obviously fallen here recently or been carried down from the plateau, and we were reduced to low gear to make any headway at all on it.

Shortly before eight o'clock in the morning Jackstraw brought the Citroen to a halt, and as the roar of the big engine died the deep moaning of the wind, a wind carrying with it a rising wall of ice and snow, swept in to take its place. Jackstraw had drawn up broadside on to the wind and the slope of the hill and I jumped down to rig up a canvas shelter extending out from the cabin: it was nothing elaborate, just a triangular sheet of proofed canvas attached to the top of the cabin and the cleat of a caterpillar track on its vertical side, with its apex stretched out to a spike hammered into the surface of the ice-cap: there was no room for us all within the cabin at meal-times, I wanted some protection when we kept our 8 a.m. radio schedule with Hillcrest, and, in particular, it was time that Zagero and Levin had some relief from their sufferings. They had ridden all night on the tractor sled, under the guard of either Jackstraw or myself, and though the temperature was now only a few degrees below zero and though they were sheltering under a mound of clothing, nevertheless they must have spent a miserable night.