The Science of Discworld Revised Edition

float on top of large, essentially solid plates, and those plates can be driven apart by upwelling magma. (Oh, but mostly by convection in the mantle. Jeffreys didn’t know what we now know about how the mantle moves.) There are about a dozen plates, ranging from 600 miles (1000 km) across to 6000 miles (10,000 km), and they twist and turn. Where plate boundaries rub against each other, sticking and slipping and sticking and slipping, you get a lot of earthquakes and volcanoes. Especially along the ‘Pacific rim’, the edge of the Pacific Ocean up along the west coast of Chile, central America, the USA, along down past Japan, and back round New Zealand, which is all the edge of a single gigantic plate. Where plate boundaries collide you get mountain ranges: one plate burrows under the other, lifting it up and crushing and folding its edges. India was once not part of the main Asian continent at all, but came crashing into it, creating the world’s highest mountain range, the Himalayas. India hasn’t fully stopped even now, and the Himalayas are still being pushed up by the force of the impact.

SEVENTEEN
SUIT OF SPELLS

    A FIGURE WAS Frogmarched through the early-morning corridors, surrounded by the senior wizards. It wore a long white nightshirt, and a nightcap with the word ‘Wizzard’ embroidered, inexpertly, on it. It was Unseen University’s least qualified but most well-travelled member, usually away from something. And it was in trouble.
    ‘This won’t hurt a bit,’ said the Senior Wrangler.
    ‘It’s right up your street,’ said the Lecturer in Recent Runes.
    ‘It’s on a log and in your face,’ explained the Dean.
    ‘That isn’t what H EX said, is it?’ said the Senior Wrangler, as the sleepy figure was hustled around a corner.
    ‘Very similar, but what H EX said made less sense,’ said the Dean.
    They hurried across the lawn and barged through the doors in the High Energy Magic Building.
    Mustrum Ridcully finished filling his pipe, and struck a match on the dome of the Project. Then he turned, and smiled.
    ‘Ah, Rincewind,’ he said. ‘Good of you to come.’
    ‘I was dragged, sir.’
    ‘Well done. And I have good news. I intend to appoint you Egregious Professor of Cruel and Unusual Geography. The post is vacant.’
    Rincewind looked past him. On the far side of the room some of the junior wizards were working in a haze of magic that made it hard to see exactly what it was they were working on, but it looked almost like … some sort of skeleton.
    ‘Oh,’ he said. ‘Er … but I’m very happy as assistant librarian. I’m getting really good at peeling the bananas.’
    ‘But the new post offers you room, board and all your laundry done,’ said the Archchancellor.
    ‘But I get that already, sir.’
    Ridcully drew leisurely on his pipe and blew out a cloud of blue smoke.
    ‘Up until now,’ he said.
    ‘Oh. I see. And you’re about to send me somewhere really dangerous, yes?’
    Ridcully beamed. ‘How
did
you guess?’
    ‘It wasn’t a guess.’
    Fortunately the Dean had been forewarned and had grabbed the back of Rincewind’s nightshirt, and so he was ready. The wizard’s bedroom slippers skidded uselessly on the tiles as he tried to make for the door.
    ‘It’s best to let him run for a little while,’ said the Senior Wrangler. ‘It’s a nervous reaction.’
    ‘And the best thing is,’ said Ridcully, to Rincewind’s back, ‘that although we are sending you to a place of immense danger where no living thing could possibly survive, you will not, in so many words, actually
be
there. Won’t that be nice?’
    Rincewind hesitated.
    ‘How many words?’
    ‘It’ll be like being in a … story,’ said the Archchancellor. ‘Or … or a dream, as far as I can understand it. Mister Stibbons! Come and explain!’
    ‘Oh, hello, Rincewind,’ said Ponder, stepping out of the mist and wiping his hands on a rag. ‘Twelve spells H EX has amalgamated for this! It’s an amazing piece of thaumaturgical engineering! Do come and see!’
    There are creatures which have evolved to live in coral reefs and simply could not survive in the rough, tooth-filled wastes of the open sea. They continue to exist by lurking among the dangerous tentacles of the sea anemone or around the lips of the giant clam and other perilous crevices shunned by all sensible fish.
    A university is very much like a coral reef. It provides calm waters and food particles for delicate yet marvellously