And then we waited. Massing there - for we were now overcrowded and uncomfortable - on the inhabited part of our world, we came to think in this way: that at least the wall, that always visible reminder of our situation, was a proof that we had a future. Our planet had a future.

The time that passed then seemed long to us, and it was; but it was slowed, as well, by the events and thoughts that packed it. Our lives, from being easy, had become hard, the ideas that had inhabited our minds without being questioned were each one tested and - so far had everything changed for us - for the most part set aside.

The crops we had grown and that we were known for in all the near planets no longer thrived. The beasts we had understood and who understood us dwindled and went, and we had new strains of animal who, because their habits were to withstand hardship and threat, did not respond to us lovingly. We had not known how much of the happiness of our lives had been because, as we went among the fields and into the wilder places, we had always been greeted by affectionate creatures. I remember how I and some other representatives of cantons and provinces went out from a town we had used as a meeting place, into a valley we were accustomed to walk in for relaxation after our discussions; and where there had been a fresh bright green, and running streams, and light, quick, playful animals, there were hillsides covered with short, rough greyish plants and rocks growing new species of lichen, grey and thick, like fur - and there was a herd of heavy-shouldered, heavy-jawed cattle, all facing us, their hours lowered, great hooves planted solidly. And, as we stood, trying not to be dismayed, because we had learned to fear our grief, the greyish-brown of their shaggy hides lightened to silvery grey. The air was shedding greyish crumbs. We put out our hands and saw them fill with this rough grey substance. A grey sky seemed to lower itself, pulled down by the weight of itself. We stood there, shivering, pulling close the new clothes Canopus had told us to use, thick and warm and not easy to move about in, and we were there a long time, despite the cold, knowing that we needed such moments of sharp revelation so that we might change inwardly, to match our outward changes.

That part of our world beyond the wall was now grey and gelid and slow and cold, and filled with the creatures of the cold. First it was all bitter frosts, and flaking and then splitting stones, so that whole mountains changed their aspect, becoming littered and loose; and lowered and sullen skies, where clouds had become thick and dark - and then the snows came, showers and squalls of snow, and after that storms that raged a day, and then days at a time. Everything beyond our wall was white, and the new animals came crowding down towards us, their coats dragging with snow, their eyes looking sullenly out from the snow on their faces. But the snows melted, leaving the greys and the browns, and then came again - and again; and did not melt so quickly, and then did not melt at all.

Canopus said to us that we, the Representatives, should walk around our planet on the top of the wall. About fifty of us, then, set out; and Canopus came with us. The task took us almost a year. We walked into, not with, the revolving of the planet so that the sun always rose ahead of us, and we had to turn ourselves around when we wanted to see how the shadows gathered at nightfall. Because the top of the wall for the greater part of its way was so narrow, we walked no more than two or three abreast, and those at the back of this company had it brought into us how small and few we were under skies that on our right were packed with snow clouds. On the other side of the wall, but far down towards the pole, the skies were often still blue, and sometimes even warm, and down there were the greens and browns of a summery land, and the streams were quick and lively. To our right the grey and dour landscape was obscured again and again by snow. We could see that the whiteness of cold had claimed the far mountains on our right, and was covering the foothills and spreading out down the valleys. And the winds that come pouring down from there hurt our lungs and made our eyes sting, so that we turned our heads away and looked down over the part of our world that still said to us, Welcome, here nature is as warm and as comfortable as your flesh. But Canopus kept directing us - gently, but making sure we did it - to look as much as we could into the world of cold.

And so we went, day after day, and it was as if we walked into a spreading blight, for soon, even on the left side of the wall we saw how grasses shrank and dimmed and vegetation lost its lustre, and the skies lowered themselves with a white glare somewhere behind the blue. And on the right the snows were reaching down, down, towards us, and our familiar landscapes were hard to recognize.

There was a day that we stood all together on our barrier wall, looking up into the freezing immensities, with Canopus among us, and we saw that the enormous heavy animals that Canopus had brought us from another of their planets were crowding close in to the wall. They massed there, in vast herds, with the snow driving down behind them, and they were lifting their great heads and wild trapped eyes at the wall, which they could not cross. A short way ahead of us was a narrow gap which we had closed with a sliding door half the wall's height.

Canopus did not have to tell us what we must do. Some of us went down the side of the wall on to the rough soil, where the grasses had long since gone, leaving a thin crust of lichens, and pulled back the gates. The herds lifted their heads and swung their horns and trampled their feet in indecision, and then saw that this was their deliverance - and first one beast and then another charged through the gap, and soon from all over the frozen lands came charging and thundering herds of animals, and they all, one after another, went through the gap. What heavy clumsy beasts they were! We could never become accustomed to their mass and weight and ponder-ousness. On their heads were horns which at their base were thicker than our thighs, and sometimes they had four and even six horns. Their hooves left behind prints that would make small ponds. Their shoulders, to support these crests and clubs of bone, were like the slopes of hills. Their eyes were red and wild and suspicious, as if their fate was to query forever what had ordained them to carry such weights of bone and horn and meat and hair, for their coats hung down around them like tents.

These herds passed through the gap in our wall, taking twenty of our days to do it, and soon there were none of these beasts of the cold in that part of our world that was doomed to be swallowed by the cold. They were all in the more favoured parts - and we knew, without Canopus having to say anything to us, what it meant.

Had we really imagined that our guardian wall would contain all of the snow and ice and storm on one side of it, leaving everything on the other side warm and sweet? No, we had not; but we had not, either, really taken into our understandings that the threat would strike so hard into where we now all lived... into where we were crowding, massed, jostling together, with so much less of food and pleasantness that our former selves, our previous conditions, seemed like a dream of some distant and favoured planet that we only imagined we had known.

We stood there, looking into hills and valleys where grass still grew, though more thinly, and where the movement of water was still quick and free; we saw how the herds of animals of the cold spread everywhere, making our ears ring and hurt with their savage exulting bellowing because they had found some grass. We were a company of thin yellow light-boned birdlike creatures, engulfed in the thick pelts of the herds, wildly gazing at a landscape that no longer matched us. And, as we had taken to doing more and more, we gazed up, our eyes kept returning to the skies, where the birds moved easily. No, they were not the small and pretty birds of the warm times, flocks and groups and assemblies darting and swirling and swooping as one, moving as fast as water does when its molecules are dancing. They were the birds of this chilly time, individual, eagles and hawks and buzzards, moving slowly on wings that did not beat, but balanced. They too had heavy shoulders and their eyes glared from thick feathers, and they circled and swept about the skies on the breath of freezing winds that had killed our familiar flocks sometimes as they flew; so that, seeing the little brightly coloured bodies drop from the air, we had looked up and imagined we could see, too, the freezing blast that had struck them down out of the sky. But they were birds, these great savage creatures; they could move; they could sweep from one end of a valley to the other in the time we could hold a breath. We had once been as they were, we told ourselves, as we stood there on the wall slowed and clumsy in our thick skins - the wall which, on the side towards the ice, was dimmed and clouded, no longer a brilliant shining black, but shades of grey. Frosted grey.