How to Recognize a Witch

From The Witches by Roald Dahl (excerpt Chapter 3)

The next evening, after my grandmother had given me a bath, she took me once again into the living-room for another story.
'Tonight,' the old woman said, 'I am going to tell you how to recognize a witch when you see one.'
'Can you always be sure?' I asked.
'No,' she said, 'you can't.  And that's the trouble. But you can make a pretty good guess.'
She was dropping cigar ash all over her lap, and I hoped she wasn't going to catch on fire before she told me how to recognize a witch.
'In the first place,' she said, 'a REAL WITCH is certain always to be wearing gloves when you meet her.'
'Surely not always,' I said. 'What about in the summer when it's hot?'
'Even in the summer,' my grandmother said. 'She has to. Do you want to know why?'
'Why?' I said.
'Because she doesn't have finger-nails. Instead of finger-nails, she has thin curvy claws, like a cat, and she wears the gloves to hide them. Mind you, lots of respectable women wear gloves, especially in winter, so this doesn't help you very much.'
'Mamma used to wear gloves,' I said.
'Not in the house,' my grandmother said. 'Witches wear gloves even in the house. They only take them off when they go to bed.'
'How do you know all this, Grandmamma?'
'Don't interrupt,' she said. 'Just take it all in. The second thing to remember is that a REAL WITCH is always bald.'
'Bald?' I said.
'Bald as a boiled egg,' my grandmother said.
I was shocked. There was something indecent about a bald woman. 'Why are they bald, Grandmamma?'
'Don't ask me why,' she snapped. 'But you can take it from me that not a single hair grows on a witch's head.'
'How horrid!'
'Disgusting,' my grandmother said.
'If she's bald, she'll be easy to spot,' I said.
'Not at all,' my grandmother said. 'A REAL WITCH always wears a wig to hide her baldness. She wears a first-class wig. And it is almost impossible to tell a really first-class wig from ordinary hair unless you give it a pull to see if it comes off.'
'Then that's what I'll have to do,' I said.
'Don't be foolish,' my grandmother said, 'You can't go round pulling at the hair of every lady you meet, even if she is wearing gloves. Just try it and see what happens.'
'So that doesn't help much either,' I said,
'None of these things is good on its own,' my grandmother said. 'It's only when you put them together that they begin to make a little sense. Mind you,' my grandmother went on, 'these wigs do cause a rather serious problem for witches.'
'What problem, Grandmamma?'
'They make a scalp itch most terrible,' she said. 'You see, when an actress wears a wig, or if you or I were to wear a wig, we would be putting it on over our own hair, but a witch has to put it on to her naked scalp. And the underneath of a wig is always very rough and scratchy. It sets up a frightful itch on the bald skin. It causes nasty sores on the head. Wig-rash, the witches call it. And it doesn't half itch.'
'What other things must I look for to recognize a witch?' I asked.
'Look for the nose-holes,' my grandmother said. 'Witches have slightly larger nose-holes than ordinary people. The rim of each nose-hole is pink and curvy, like the rim of a certain kind of sea-shell.'
'Why do they have such big nose-holes?' I asked.
'For smelling with,' my grandmother said. 'A REAL WITCH has the most amazing power of smell. She can smell out a child who is standing on the other side of the street on a pitch-black night.'
'She couldn't smell me,' I said. 'I've just had a bath.'
'Oh yes she could,' my grandmother said. 'The cleaner you happen to be, the more smelly you are to a witch.'
'That can't be true,' I said.
'An absolutely clean child gives off the most ghastly stench to a witch,' my grandmother said. 'The dirtier you are, the less you smell.'
'But that doesn't make sense, Grandmamma.'
'Oh yes it does,' my grandmother said. 'It isn't the dirt that the witch is smelling.  It is you. The smell that drives a witch mad actually comes right out of your own skin. It comes oozing out of your skin in waves, and these waves, stink-waves the witches call them, go floating through the air and hit the witch right smack in her nostrils. They send her reeling.'
'Now wait a minute, Grandmamma...'
'Don't interrupt,' she said. 'The point is this, when you haven't washed for a week and your skin is covered over with dirt, then quite obviously the stink-waves cannot come oozing out nearly so strongly.'
'I shall never have a bath again.' I said.
'Just don't have one too often,' my grandmother said. 'Once a month is quite enough for a sensible child.'
It was at moments like these that I loved my grandmother more than ever.