Stoneseed, Chapter 1

The catacombs served as a reminder that as long as there had been any history at all, there had been Dwarven history: the oldest passages were said to be as old as time itself, and even the newest dated from the late Old Age (or perhaps the early New Age-- it was often difficult to tell).

The catacombs also served as a reminder that as long as there had been Dwarves, they had had skulls. The walls of this region-- a forgotten tomb, perhaps, or maybe simply the favoured haunt of someone with a particularly morbid hobby-- were lined with them, floor to ceiling, five and a half feet vertically and already a kilometre horizontally, with no immediate end in sight. There were branches in the unlit stone passageway, of course, but these contained little of interest, in comparison to what Acier Faussaire knew waited for him at the end of this particular passage.
'How much further?' he asked, pouring a little more willpower into the light his Sorcery had created and smiling a little with relief as the shadows around him retreated.
'Not far,' Avis Partant, his guide, replied. Avis was somewhere between a meter and one and a half meters tall, around average height for a Dwarf, with pale skin made paler from lack of sunlight and coarse hair a deep, dark brown to match his eyes. He rarely left the catacombs, although this meant he was one of the more qualified guides to this region of them. He was a year or two older than Acier, and although the two of them weren't particularly close they had each counted the other among their friends for several years, and Acier had known Avis for long enough to know a lot about him. It had been some time since they had last seen one another; Acier swore Avis' voice sounded different, but he couldn't put his finger on how exactly.

As they continued forwards, Acier's head was steadily filled with a high-pitched, persistent whine. The first time he had heard it, some years ago now, he'd thought it was simply some strange new insect; after a few hours he'd assumed it would go away of its own accord soon.

When, three days later, it refused to do so, he consulted Deeproot's resident healer. She'd confirmed it was tinnitus, but had been unable to determine the exact cause; there seemed to be no issue with earwax buildup and no infection, nor were his eardrums perforated. The exact cause of his tinnitus-- and occasional attacks of vertigo-- was still unknown.

It never outright stopped, either: the best Acier could do was keep his attention on other things, such as what was waiting for him up ahead.
Ahead, Avis turned to him and halted, waiting for his fellow Dwarf to catch up.
'You okay, Acier?' he asked.
'Yeah,' Acier said, 'I just... I don't like these tunnels. They give me the creeps.'
'We're Dwarves,' Avis said. 'We're built for tunnels.'
'Maybe you were,' Acier said. 'Give me a sky over my head any day, not a few metric tons of rock. The sky doesn't ever look like it's about to collapse.' He came up alongside Avis and the two of them continued along the narrow passageway. The walls were still staring at him, although the skulls were beginning to give way to an assortment of other bones. The heaps of ribs and femurs and hips didn't exactly suggest an expensive burial.
'This passage goes back to the Mageblight,' Avis explained. 'The bodies here are of Blight victims-- note the unusual deformations.'
'Huh,' Acier said. So these bodies had been the victims of misguided healing Sorcery-- magic that healed in the short term but killed in the long run. It really didn't make him feel better about being there. 'Why are the skulls buried somewhere else?'
'To keep them from coming back,' Avis said.

Acier shuddered. 'Wait. Isn't the Golem newer than the Mageblight? Like, much newer?'
Avis nodded. 'Newer passages are usually further out from routes down into this place.'
'Why would whoever built this thing pick a spot right near Blight corpses?'
Avis began to explain, but Acier only caught half of it: the steady whine in his ears made it difficult to focus on occasion. As best he could tell, however, the bones were examined by the Golemancer for some purpose.

'Is it much further now?' Acier asked, trying to shut out the persistent noise in his ears.
'Just a few hundred metres,' Avis said. 'I don't like this part of the catacombs. It sounds wrong.'
'Wrong?'
'Wrong.'
Acier was beginning to grow exasperated. 'Wrong?'
'Wrong,' Avis said, his tone unchanged. He was autistic, after all; clear communication wasn't always his strong point.
'Is there a sound here that there shouldn't be, or is it something else?' Acier asked. This wasn't his first time in the catacombs with Avis as his guide-- he knew by now the best way of wording things.
'Something else,' Avis said, slowing down.
'What else is there?' Acier asked, puzzled.
'This,' Avis insisted. 'It sounds wrong!'
'Sounds,' Acier murmured. 'Sounds, sounds, sounds... is there an echo, or--'
'Echo,' Avis said. 'There's an echo there shouldn't be.'
'I say we worry about that later,' Acier said. 'We get the Golem, we head back to the surface, and we send a few people down to look into this echo. That okay?'
'Okay,' Avis said. 'The workshop is in the next door on the right.'
Acier listened out for the echo as he approached, but heard nothing save for the persistent whine of his tinnitus and his own footsteps.

The bones thankfully didn't reach the whole way to the door frame: an area had been cleared of them, bricked up, and later cleared. Several stone bricks were still in fact scattered about the place, and a thin film of dust lay over everything for several feet around.
'How did you find this place?' Acier asked, sweeping his shoulder-length blonde hair away from his thin, Quartz-coloured face.
'No bones,' Avis replied.
Acier nodded: no bones here but bones on either side seemed to suggest someone had cleared away this spot at some point. Factor in the brick work, and...
'I don't know why nobody saw it before,' Avis admitted.
'There are a lot of blocked-off passages in this place,' Acier said. 'You're good at finding your way around the place, for whatever reason.'
'Maps,' Avis said. 'I map the place in my free time. Helps me to think.'
'You ever thought about selling your maps?' Acier asked, stepping through the cramped doorframe and into the workshop.
'I prefer this,' Avis said.
'Being down here?' Acier said, disbelieving.
'Being down here.'

Shaking his head, Acier examined the room he now found himself in. It seemed to be a fairly sizeable complex: the large entry chamber had a small doorway to either side, plus a larger one directly ahead, which seemed to lead to some form of balcony. The stone walls were smooth, and the ceiling had once been; at some point in the past thousand or so years, however, it had split and cracked and crumbled, showering the cheap metal furniture in dust and debris. Several bulky, leatherbound tomes were visible, half-buried; their covers were inset with gemstones, but their pages had been torn out and seemingly burned. From somewhere nearby came the steady drip-drip of water, barely audible over his tinnitus.

In fact, Acier realised, a lot of the furniture appeared to have been moved roughly from against walls, as though the place had been searched.
'What happened here?' Acier murmured.
'Someone ransacked the place and sealed it up,' Avis stated plainly; Acier recalled his guide didn't understand rhetorical questions.
'Why?'
'I don't know,' Avis stated. 'I knew you'd pay for a late Old Age workshop once used by a Golemancer.'
'With an intact Golem,' Acier smiled. 'You've outdone yourself on this find, Avis. If its last command was something useful, I'm paying double.'

Golems were Acier's strong point, to a degree: the Faussaire family had always had some talent for them, but it manifested in him far weaker than in the rest of his family. It had taken him years to get the hang of it, and he was far from a master. And it wasn't just talent, either: it was discipline. Once or twice he'd contracted out his Golems to dig wells, travelled to farm towns in the Human Kingdoms, set them up, and forgotten to give them instructions on when to stop.

This was the chief problem with Golems: they followed instructions to the letter, especially when those instructions had some critical flaw in them, as Acier's often did.

The alternative was to use Automata: These were far more complicated. They required a fully jointed framework to be built and a core, generally made from solid gold (which was, after all, cheap, plentiful and easy to work with), onto which detailed instructions had to be painstakingly carved, rune by rune. Order magic was like that sometimes.

Still, Acier had to admit Automata had their advantages: they could be programmed for speech, for example, and to perform multiple complex tasks, switching between them as necessary. With Golems, you had to clear them and give them fresh instructions every time. Chaos magic had its downsides, but Acier certainly preferred it. And besides, it was in his blood; Alchemy had to be learned, but Sorcery was inherited.

Acier's line of thought was interrupted by the steady whine of his tinnitus. He turned to Avis. 'Does anyone else know about this place?'
'I claimed the finder's fee with the Historian's Guild, too,' Avis explained. 'They should be sending a representative down any day now.'
'Down here?' Acier asked. 'As in the catacombs or as in Deeproot?'
'Deeproot,' Avis said. Deeproot was at this point several dozen metres over their heads. It wasn't the largest fortress in the Dwarven Mountains, but it was fairly sizeable.
'They'll be expecting to meet with me, then,' Acier said.
'I found it, but you can explain it,' Avis agreed. 'They're sending an old friend of mine-- I don't think he knows about Golems. Alchemy is more his thing.'
'I've heard they're yet to hear of the whole "right man for the right job" thing,' Acier nodded. 'Plus this way I might get some Gold out of this whole thing, even if the Golem proves useless. How do you know this guy?'
'I corresponded with him back when I considered moving to Antliss and studying at the College of Alchemy,' Avis explained. 'The college didn't really know how to handle autistic students, but he'd been close to one in the past, so they put me in touch with him directly. We wrote a few letters back and forth, he explained what the place was like, and how little they tried to accommodate Perl and her needs, and how she eventually dropped out... and I decided against going. Besides, I-- I wasn't comfortable leaving Deeproot.
'This was back when I was-- figuring out a little about myself,' he continued hesitantly. 'He knows about my name and my pronouns, at least. One of the last few letters between us was me updating him on that whole thing.'
Acier nodded. 'Anyway, this Golem-- where is it?'
'Big room,' Avis said, turning to one side and starting for one of the smaller doorways. Acier frowned, and made his way along the passageway towards the larger one: it opened out onto a balcony, as he had been expecting. There was no way down to the workshop itself-- presumably that was what the other two doors were for-- but it offered him a view.

The room was dominated by a large worktable, wider than it was long, covered in clay that had been dry for centuries: this was stone rather than metal and was covered in runes and symbols, engraved with haste more so than skill. One corner had been broken off, but aside from this it was largely intact. Off to the left was a metal desk, atop which were the remains of several ceramic arms. Acier had seen these before, and had in fact used one himself, when he was apprenticed to a Golemancer in Low Icevault; it was designed for copying instructions.

After all, priming a Golem for a complex task could require hours of speaking to it, maintaining focus the entire time; one slipup, and you'd have to start over. Luckily, it was possible to write out instructions, place them inside the Golem, and animate it; these scribe Golems were designed to automate the process of writing out instructions for basic tasks, to be inserted into mass produced Golems for general sale. Apparently whoever had once used this workshop had supported their Golemancy through this means.

On the other side of the room was a huge heap of dry clay, same as on the table: the brownish mass was a little more gruesome, however, as several ceramic limbs were visible protruding from it.

Trying his best to ignore the steady whine in his ears, Acier stepped back and made his way into one of the side passages, down the stairs, and into the workshop itself. He found Avis standing in the center of the room, flapping his hands uncertainly: he always stimmed like this when he was excited about something, Avis recalled.
'How do you know there's a Golem in here?'
'Golem in here,' a strange voice said. It was deep and sounded dry as a desert.
'That wasn't you,' Acier realised with a start.
'Wasn't you,' the voice echoed.
'So someone programmed a Golem for speech...'
'Golem for speech...'
'They did,' Avis agreed. 'It must be buried somewhere in the pile.'
'In the pile,' the Golem echoed, and then added, to the surprise of Acier: 'Why are you calling me "it"? My creator always referred to me as "they".'
'You can... speak,' Acier realised. 'Highest, Avis, they can speak! They can... Do you have any idea how complicated they must be, to be able to speak like that?'
'Speak like that,' they echoed.
'Echolalia,' Avis noted. 'I know someone with that over in Ristion.'
'Over in Ristion,' The Golem said.
'You've a pen pal in the Human Kingdoms?' Acier asked, surprised.
'Human Kingdoms.'
'And another in the Townships,' he said. 'Iau Sandia. They're both autistic, same as me.'
'Same as me.'

'Golem?' Acier asked. 'Where are you?'
'Where are you?' they said. 'I don't know. It is dark.'
'They're buried in all that,' Acier said, gesturing towards the heap of debris and limbs. 'We just need some kind of tool or... or something, to get them out.'
'Get them out.'
'No,' Avis said, 'we don't.'
'We don't.'
'We don't?' Acier asked, puzzled.
'We don't?' the Golem echoed.
'Why don't we?' Acier frowned. 'We can't leave it in there, so... it's something else, right?'
'Something else, right?'
'Golem,' Avis stated, 'dig.'
'Dig,' the Golem echoed.

It took Acier a moment to realise anything was happening, but soon enough the sounds of something scraping reached his ears, barely louder than the steady whine of his tinnitus. The heap of clay began to shake slightly, and after a few minutes an arm emerged from it, followed by--

Followed by a broken stump of ceramic, at the center of which was a spur of stone.
'So that's why they built their workshop here,' Acier murmured. 'This is a Golem with a... skeleton. I never thought of that.'
'Thought of that,' the Golem said.
'Golem,' Acier realised, 'your creator put a lot of time into you... stands to reason they gave you a name.'
'You a name,' they said. 'She did not.'
'Maybe we should name you for the same of convenience,' Acier decided.
'Sake of convenience. No,' they stated, their voice still muffled by the debris as they struggled free. 'I chose the name "Clay" for myself.'

It was at this point that their head finally emerged, followed by their shoulders: Avis rushed forwards to pull them free of the debris, and Acier joined him. After a few moments of struggling, they freed Clay from their tomb of so many centuries. Acier realised as they stepped free from it that the tangle of limbs he'd seen protruding from it had all been theirs.

They looked to be about a meter in height; Acier wouldn't be surprised if they were a meter exactly. Their skin-- if it could be called that-- was the colour of copper, and shiny, suggesting a glaze of some sort had been applied before they were fired. They were chipped in several places, and the spur of bone protruding from their stump of an arm was far from the only damage they had received over the decades: the glaze had seemingly been scratched away from their joints from sheer use, and a portion of their head had split open; the resulting patch of matte orange unglazed material looked a little like a large birthmark. Their body was nondescript, but their facial features were distinctly Dwarven and finely carved (although their nose was chipped). Their eyes shone with a piercing blue light, and as the same glow spilled forth from their mouth as they opened it to speak.
'Where is my creator?'
'Clay,' Acier asked, 'do you know how long you've been down here?'
'Been down here,' Clay said. 'No. I was designed to keep track, but I was... damaged.'
'When?' Acier asked, still amazed by the fact that he was having a conversation, an actual conversation, with a thousand year old (perhaps even older-- nobody actually knew when the Old Age ended and the New Age began, after all) Golem. He'd been expecting to simply have it repeat its last orders, maybe find something interesting out on mining techniques or bricklaying when it was created, but... it could speak. And they weren't an it, either, Acier corrected himself-- they were a they. Clay was an intelligent piece of history-- the things they might learn from such a being!

'Acier?' Avis asked. 'If there's nothing more to gain here...'
'Gain here...'
'We should leave,' Acier agreed. 'Clay, are you coming?'
'You coming? Yes,' Clay said. 'I witnessed the death of my creator and was not given the offer of finding a new master; one of you shall be sufficient.'
'Avis, you mind?' Acier asked.
'Avis, you mind?'
'Okay,' Avis said.
'Okay,' Clay echoed.
They stood there in silence for a few moments; Acier's head slowly filled with the steady, insect-like whine of his tinnitus.
'Back up to the surface, then?' he said. 'Nothing much else to see here-- the place was ransacked, after all.' Out of curiosity, he asked: 'Clay, who did this?'
'Who did this?' Clay replied. 'The Ancienne. My master had many enemies.'
'The Ancienne...' Acier murmured. 'I think I've heard of them.'
'Heard of them,' Clay said.
'I've found their outposts,' Avis said. 'They're extremists from the last days of the Old Age-- believed magic was the cause of all the world's problems.'
'The world's problems.'
Acier finished his brief examination of the workshop before replying: as he suspected, anything else of any real interest had long ago been destroyed. 'Stands to reason they'd target a Golemancer powerful enough to create someone like Clay here.'
'Like clay here,' Clay repeated.

They stepped back out into the corridor: Avis, then Clay, then Acier. Avid led them back through the tunnels, and soon enough they were surrounded by bones once again. He hadn't been maintaining a steady flow of willpower to the orb of light he had created, but thanks to the steady glow of Clay's eyes this wasn't much of a problem. Still, it meant the path behind them was pitch dark.
'Is that strange echo still there?' Acier asked.
'Still there?'
'We're getting closer to it,' Avis said. 'It's a sound that shouldn't be here. It wasn't here last time-- there's something else here.'
'Else here.'
'Avis,' Acier said, 'neither of us is armed. If someone tries to take Clay from us...'
'Clay from us...' Clay said. 'I am capable of self-defense-- should we come under attack I shall protect my master and my master's companion.'
'You can fight?' Acier asked, surprised.
'You can fight? I am capable of self-defense,' Clay repeated.

There was a sudden blast of air along the passage from the way they were heading, whipping Acier's long (on him-- it was intended for a human, but he found if he rolled the sleeves up a little it was an alarmingly comfortable fit) out behind him. He threw up an arm to shield his eyes from the miniature dust storm that followed, and--

And screamed in shock as the skeletons lining the walls began to move. They twitched their way down from the walls and began to form up into coherent figures that were... something other than Dwarven. Here a broad figure, a pair of ribcages splayed outwards, with no arms or head, staggering sightless towards them; there a ball of limbs, inching itself forwards with each convulsion.
'Have I ever mentioned how much I hate skeletons?' Acier asked. 'Because I really, really can't stand them.
'Can't stand them,' Clay stated. 'Master's companion, get behind me.' They stepped past Avis, putting their ceramic from between the pair of Dwarves and the advancing monstrosities. The ones nearer they seemed to get larger as they went further and further back into the passageway: near the front were snakes and spiders made from fingers and toes, but towards the back was a great behemoth of ribs and hips, a massive figure formed from at least a dozen complete skeletons.
'Clay?' Acier asked uncertainly. 'Are you going to... do anything?'
'Do anything?' Clay echoed, the blue glow from their mouth growing brighter and then dimmer as their lips moved. 'Certainly, master.'

They stepped forwards and raised their hand, palm out, planting their legs firmly on the stone floor as they dropped into a defensive stance. Nothing happened for a few moments, and then the Golems, one by one, began to crumble.

Acier decided to risk checking his Magesense. To Alchemists, there was no risk involved in this: they could use the ability whenever they felt like it. To Sorcerers such as Acier, however, it carried a risk: each time it was used, it became harder and harder to return to the usual five senses; several elderly Sorcerers were trapped permanently seeing the world through either Magesense or Lifesense, another similar power. As such, it was an ability to be used sparingly; it was perhaps the only aspect of magic where Alchemy had objective Benefits over Sorcery.

Acier allowed his Magesense to activate, and his viewpoint of the world abruptly altered. He could see several feet in all directions, but everything was white and shapeless-- save for Sorcery, which was picked out in red, and Alchemy, which was blue. Clay was visible as a solid block of red, and waves of the same pulsated out from their extended arm; there was also the faint red glow of the ball of light Acier was using, and he couldn't help but notice a curious smudge of blue around Avis's neck. Turning his attention further outwards, he noticed the bone Golems were...

Purple, Acier realised. Sorcery and Alchemy combined into one: the work of a Bifold Mage. Combining the two branches of magic wasn't easy: without incredibly skilled hands, the order of Alchemy and the chaos of Sorcery combined into greater chaos-- often with highly destructive results.

Still, even their magic seemed to be no match for Clay's: Acier realised that the Golem's defensive Sorcery could only be void, the fifth element, known to some as anti-magic. It was cancelling out the complex interwoven Golemancy and Automata creation that had gone into their monstrous assailants, returning them to inert and motionless bones once again; one by one they collapsed, their purple glow fading, as Clay strode forwards.

Acier was about to shut out his Magesense when he realised there were a few specks of purple approaching from the opposite direction.
'There are more coming from behind!' he said, his regular senses forcing their way back in and driving out his Sorcerous view of the world.
'From behind!' Clay said, lowering his arm as the last Golems collapsed. Acier noticed in the glow from his ball of light that Clay's hand now hung limply: apparently it wasn't immune from the void magic they had just used.
'Clay,' Acier said, 'can you deal with those too?'
'With those too? No,' they said. 'Not until my hand is functional once more.'
'Run?' Avis offered.
'Run?' Clay suggested.
'Run,' Acier nodded.
'Run.'

The three of them took off at a steady sprint: Avis took the lead, with Acier hot on his heels and Clay no more than a metre behind. They had one advantage over the assorted horrors behind them: they were actually capable of running. The skeletal Golems were by and large limited to hobbling and scraping, clawing their way along the walls and the floor; the smaller ones, the spiders and the snakes, could catch up, but could just as easily be booted back into the oncoming crowd by a well-placed kick from Clay.

Before long the walls went from assorted bones to rows upon rows of skulls. Fear drove Acier to run faster and faster, finding new and unusual reserves of stamina as the narrow passageway blurred past. However, he couldn't keep up such a strenuous pace forever, and after a time he found himself flagging: Clay's heavy footfalls were mere centimetres behind him, the steady pounding of his feet adding to the persistent whine in Acier's head.

'Clay?' Acier called. 'How close are the other Golems?'
'Other Golems,' Clay said. 'A few feet.'
'Feet?' Acier asked.
'Feet?' Clay echoed.
'They're another measurement,' Avis called.
'Another measurement.'
'Another measurement of... what?' Acier asked. He was beginning to grow exhausted-- his legs ached like they'd never ached before and he wasn't quite sure his feet were still where they should be. If anything, his tinnitus was getting worse; the endless whine was almost louder than the steady pounding of Clay's feet.
'Of what?'
'Of how big,' Avis called.
'How big.'
'Distance?' Acier asked.
'Distance?'
'Of how big,' Avis agreed.
'How big.'
'Avis!' Acier realised. 'Are there any passages around here too narrow for the bone Golems to fit through? We need to give them the slip.'
'Them the slip,' Clay repeated.

Avis slowed down abruptly, and Acier struggled not to run straight into him.
'Keep moving!' he urged.
'Keep moving!' Clay said.
'I can't think when I'm fast,' Avis said.
'When I'm fast.'
'You can't find us a way out of here if you're running?' Acier realised.
'If you're running.'
Avis shook his head. 'There are a lot of passageways in this area-- I need to focus.'
'Need to focus.'
'Clay?' Acier asked. 'How long until you can do your hand thing again?'
'Hand thing again,' they said. 'Not long, but the Golems will be upon us by then.'
'Come on, Avis, think!' Acier urged. 'We need to--'
'Next left,' Avis said abruptly.
'To-- next left.'

Avis darted forwards abruptly; Acier and Clay followed. They passed through an archway and out of the bones: the walls around them closed in and shifted from assorted skulls to greyish bricks.
'Clay,' Acier realised, 'can you fit?'
'Can you fit? Yes,' they said, 'but with difficulty.' It was true: their shoulders were scraping against the wall, and every few hurried steps their forehead would collide with the roof of the passage.
'This area was originally made as a shortcut by smugglers,' Avis explained. 'See the floor? They used to bring barrels through here. There's a door ahead-- second left and then third right-- that should bring us right to the external passage.'
'External passage,' Clay said.
'That comes out just outside the external part of Deeproot, right?'
'Deeproot, right?'
'Right,' Avis said. 'Just off the trade road.'
'The trade road.'

Clay still had to periodically stamp on a smaller Golem, but the sounds of the larger ones died away as Acier rushed forwards, and were soon inaudible over his tinnitus.

Abruptly, the narrow passage ended in a wall: a dead end.
'Avis?' Acier asked. 'You've brought us to--'
'No,' Avis said. 'I just need to open it.'
'To open it,' Clay echoed.
'This is a smuggler's door,' Avis said. 'Used in the middle of the New Age. I've never used it before, but I've used others like it-- One of these bricks conceals a mechanism...'
'Conceals a mechanism.'
'Clay,' Acier asked, as he watched Avis search the wall, 'why are you doing that?'
'You doing that,' Clay said. 'Doing what?'
'Repeating everything Avis and I say,' Acier said.
'And I say. I was created in my master's image.'
'I know, I know, you look like a Dwarf,' Acier nodded. 'But why the copying?'
'Why the copying?' they said. 'Because I was created in my master's image-- I speak as she spoke.'
'Echolalia,' Avis said. 'Remember my friend from Ristion? She does it too.'
'Does it too,' Clay said. 'Yes, that is the term.'

The wall in front of them clicked and slid aside: with a little struggling, the three of them managed to get through. Avis began struggling to pull it shut; Acier and Clay joined the efforts, and it slammed into place just as one or two bone Golems came into view, shambling into the soft glow of Clay's blue eyes.

'It's easy enough going from here on,' Avis said plainly. 'This is a main tunnel, after all-- part of an old mine originally, but refurbished late Old Age and then turned into an underground roadway early New Age.'
'Early New Age,' Clay said.
'Good,' Acier nodded. 'We just need to meet our friend from the guild, take both them and Clay back to my workshop, talk things over, and all of us leave rich and famous.'
'Rich and famous.'
'You said it,' Acier smiled, as the three of them strode towards the distant light of the passage up to the surface.