At first the rising heat was comfortable — preferable, anyhow, to the dry, deathly chill of the ice chasm. Suspended here in the dark, she tried to imagine she was feeling the sun on her back, rather than the soulless, sourceless heat of deep rock.

But soon the warmth became less pleasant. She felt her heart race. She spread her ears as far as they would go, lifted her tail and opened her anus flap, opened her mouth and extended her tongue — all to let her body heat escape into this cloying air.

On she walked, deeper and deeper into the dark, and still the heat gathered.

At last the breeze felt a little cooler, and the quality of the echoes from the tunnel ahead changed. Underfoot the ground sloped, suddenly, much more sharply downward.

She stopped.

She sensed the passage broadening into a wider cave. The mouth of her tunnel was set a little way above the floor of the cave. She extended her head and trunk into the empty space beyond the tunnel. The air felt much cooler, and she dropped her ears and anus flap.

With great care she worked her way down a shallow slope of scree to the floor of the cave.

She was still in complete darkness, but she could sense the great dome of the cave’s ceiling far above her, like the roof of some giant mouth.

The breeze seemed to be coming from the opposite side of the cave. But she felt wary of striking out into the darkness.

So she began to feel her way along the wall.

The soft, gritty rock was extensively scratched and scoured. She ran the sensitive tip of her trunk over furrows and grooves.

They were unmistakably the marks of mammoth tusks.

The scrapings of tusks were everywhere, even — she suspected — higher than she could reach herself. She imagined huge old Bulls reaching high up with their gigantic tusks to bring down fresh rock for their Families.

When she ventured a few paces away from the wall, she found the uneven floor littered with mammoth dung. It was obvious that the whole of this cavern had been shaped by the working of mammoths, over generations. But when she picked up some of the dung and broke it open, it crumbled, dry as dust. It was very old, and it was evident that no mammoth had been here for many years.

She used her own tusk to scrape free pebble-sized lumps of rock from the wall. She picked them up, tucked them in her mouth, ground them to sand with her huge teeth, and swallowed them. The rock’s flavor was deliciously sharp: perhaps born from an ancient volcano, this loose, ash-like rock evidently was rich in salt and other minerals the mammoths needed.

The reason for the mammoths’ presence in the cave was clear. Mammoths need salt and other minerals, as do other animals. But their tongues are not long enough to reach around their trunks and tusks to reach salt-licks, exposed outcroppings of salty minerals. So they dig them up, using their tusks to loosen the earth. This whole cavern system might once have been a simple seam of soft, salty rock into which the mammoths had dug, until at last they had shaped this giant cave and the tunnels that led to it.

Silverhair held fragments of the rock on her tongue, relishing the salty taste and the rich, ancient mammoth smell of the place, as if she were tasting the living past itself. She walked on, surrounded by the workings of her ancestors, obscurely comforted.

At last she came to a heap of scree. The fresh breeze seemed to spill from a hole somewhere above her head. It must be another tunnel.

She clambered onto the scree. Her feet scrabbled to get a foothold in the unstable mass; it took several efforts before she had raised herself sufficiently to get her forelegs over the lip of the tunnel. Then it was a simple matter to pull herself all the way in.

She turned her back on the salt cave and marched on, into the darkness.

She felt the tunnel floor rising. The walls closed around her uncomfortably; if she took a step to either side she brushed against warm rock. But, as she climbed, she felt a delicious, welcoming chill return to the air. The breeze she had followed continued to strengthen.

And, ahead of her now, she made out splinters of green-blue light.

Gradually, as her eyes adapted, she saw that the pale green glow was outlining the walls and floor and roof of her tunnel. She could even make out the larger boulders on the floor, and she was able to press forward with confidence.

At last she came to a new chamber. Like the first she had found, this chamber evidently had been hollowed out by mammoths. But this one was flooded with light. The low rocky roof of this cavern had collapsed. She could see great slabs of rock scattered over the floor, gouged cruelly by the ice, and only spires and pinnacles of rock remained. The cave now was enclosed by a roof of ice.

In some places the ice was smooth and bare. Elsewhere the roof was made of snow, with thick white pillars and balls of ice crusting its undersurface, all of it glowing blue-white. Some of the roof ice had broken off, and chunks of it lay scattered over the floor with the rock chunks. Perhaps this was an outlying tongue of a glacier, strong enough to bridge this hole in the ground, thin enough to let through the light.

But the light was very dim. The sunlight was scattered by the ice and turned to a deep, extraordinary blue, translucent, richer than any color she had seen before. Silverhair wouldn’t have been surprised to see Siros, the water-loving calf of Kilukpuk, come swimming through the air toward her, her legs reduced to stubby flippers.

She worked her way around the gouged walls. Most of the scouring was functional: simple scrapes and gouges, some ending in a ragged scar where a chunk of the salty rock had been prized away. But some of the gouges were strange: small marks grouped in compact patterns that seemed to have been made with a great deal of care. At the base of the wall she found pebbles — and even a chipped-off piece of tusk — that looked as if they had been picked up and used to shape the gouges just so.

As she stared at them, the patterns were somehow familiar.

Here was a simple series of down-scrapes — but, for a heartbeat, Silverhair could see, as if looking beyond the scrapes, a dogged mammoth standing alone in a winter storm, thick winter hair dangling around her. And here, two little clusters of scrapes became a Cow with her calf, who suckled busily.

Then she lost the images, like losing her grasp on a lush strand of grass, and there were only crude gouges in the salty rock.

The markings came from a richer time: a time when there were so many mammoths on the Island, they were forced to dig far underground in search of salty rock; and they were so secure, they had the time and energy to record their thoughts and dreams in scrapings on the walls. It must have taken a Great-Year to make these caves, she thought; but the mammoths (before now, at any rate) had never been short of time.

If only she understood what she was seeing, she thought, she might find the wisdom of another Cycle here — not songs passed down from mother to calf, but messages locked forever in the face of the rock. Lop-ear surely would have understood these images: she remembered the way Lop-ear had scraped at the frost, making markings to show her the Island as a bird would see it. Lop-ear would have been happy here, she realized: happy surrounded by the frozen thoughts of his ancestors.

But all the dung was dry and odorless, very old; and the wall markings were coated by layers of hardy lichen, orange and green, the ice-filtered light fueling their perennial growth.

It had been the scraping of mammoths that had opened up the passages she followed, even the underground caves she had found. Now it was the patient work of those long-gone mammoths that was providing her with a means of escape from the Lost. Had they known, as they dug and shaped the Earth, that their actions would have such dramatic consequences for the future?