Tunnels 02, Deeper

rock face above it.
    "We're all right," he announced, returning to where he'd left his backpack and shrugging it onto his shoulders.
    "Huh? We are what? "
    "I think it's clear," was Will's inscrutable response.
    "Yeah, clear as mud!"
    "Well, are you coming or not?" he harshly asked Chester, who stared at his friend, suspicious of the sudden change that had come over him. Will was already by the side of the canal, clipping his lantern onto his shirt pocket. Ha faced the wall for a few seconds, then began to heave himself up it. Finding foot- and hand-holds, he climbed in an arc that took him under the spluttering gaslight but over the entrance of the slow-moving canal, until he was safely on the opposite side.
    "Not the first time that's been done," he declared. He called to Chester, still on the other bank: "Come on, don't just stand there. It's a piece of cake -- not difficult to get across. Someone's chiseled out some grips."
    Chester looked indignant and impressed in equal measures. His jaw dropped, as if he was about to say something, but he thought better of it, muttering only, "Business as usual."

    * * * * *

    Although Will wasn't following any discernable path, he now seemed to be so convinced they were going in the right direction that it was Chester tagging along after him again. Marching swiftly, they moved deeper into the featureless expanse, not encountering any other landmarks, until they eventually arrived at a place where the floor became looser and began to gradually ascend. Perhaps it had something to do with the fact that the canopy above their heads was also increasing in height but, with every step the boys took, the winds around them seemed to be blowing with much greater force.
    "Phew, that's better!" Will said, running a finger around the inside of his sweat-soaked shirt collar. "Bit cooler now!"
    Chester couldn't have been more relieved that Will appeared to have pulled himself out of the appalling melancholy into which he'd sunk. In fact, he was chatting away quite normally, although it felt so much quieter without Cal there to badger them. As if his mind were playing tricks on him, Chester had the oddest feeling that the boy was still there with them. He found himself glancing around in an effort to locate him.
    "Hey, this feels sort of chalky," Will noted as they clambered up the slope, slipping and stumbling as the light-colored substrate shifted beneath them. For the last stretch, the incline had become more pronounced, and they had been forced to climb it on all fours.
    Will suddenly stopped to pluck a rock the size of a tennis ball. "Wow! A fine specimen of a desert rose ." Chester saw the pale pink blades that radiated out from a central point to the pale pink blades with his nail. "Yep, this is gypsum, all right. Nice, isn't it?" he said to Chester, who didn't have time to answer before Will was spouting forth again. "A fine example." He glanced around. "So there must have been evaporation going on here for the last century or so -- unless, of course, this was buried and it's much older. Anyway, think I'll keep it," he said, slipping off his rucksack.
    "You're going to do what? It's just a hunk of rock!"
    "No, it's not rock. It's actually a mineral formation. Imagine some sort of sea right here." Will opened his arms expansively. "As it dries up, the salts all come out of solution and... well, the rest of what you see is sedimentary. You know about sedimentary rocks, don't you?"
    "No, I don't," Chester admitted, studying his friend carefully.
    "Well, you have three classes of rock: sedimentary, igneous, and metamorphic," Will blathered on. "My favorites are sedimentary, just like we're finding down here, because there's a story in them, from the fossils you get in them. They're formed..."
    "Will," Chester said gently.
    "...formed generally on the surface, mostly underwater. Why would you find sedimentary rocks so deep in the earth? I wonder." He looked mystified at his own question, then answered it. "Yes, I suppose there must have been a subterranean lake or something here."
    "Will!" Chester tried again.
    "Anyway, sedimentary rocks are cool -- I don't mean cool as in cold, as opposed to hot, not hot like lava, which are the igneous rocks, which are..."
    "Will, stop it!" Chester shouted, becoming quite alarmed by his friend's bizarre behavior.
    "...called the first great class because they're formed from hot, molten..." Will trailed off in midsentence.
    "Get a grip, Will. What the