"Why, yes," said the Princess, "but only once in twenty-four hours, and then the dragon is turned to stone. But the griffin has dreams. The griffin sleeps at teatime every day, but the dragon sleeps every day for five minutes, and every day it is three minutes later than it was the day before." "What time does he sleep today?" asked Nigel. "At eleven," said the Princess. "Ah," said Nigel, "can you do sums?" "No," said the Princess sadly. "I was never good at them." "Then I must," said Nigel. "I can, but it's slow work, and it makes me very unhappy. It'll take me days and days." "Don't begin yet," said the Princess. "You'll have plenty of time to be unhappy when I'm not with you. Tell me all about yourself." So he did. And then she told him all about herself. "I know I've been here a long time," she said, "but I don't know what Time is. And I am very busy sewing silk flowers on a golden gown for my wedding day. And the griffin does the housework--his wings are so convenient and feathery for sweeping and dusting. And the dragon does the cooking--he's hot inside, so, of course, it's no trouble to him; and though I don't know what Time is I'm sure it's time for my wedding day, because my golden gown only wants one more white daisy on the sleeve, and a lily on the bosom of it, and then it will be ready." Just then they heard a dry, rustling clatter on the rocks above them and a snorting sound. "It's the dragon," said the Princess hurriedly. "Good-bye. Be a good boy, and get your sum done." And she ran away and left him to his arithmetic. Now, the sum was this: "If the whirlpools stop and the tide goes down once in every twenty-four hours, and they do it five minutes earlier every twenty-four hours, and if the dragon sleeps every day, and he does it three minutes later every day, in how many days and at what time in the day will the tide go down three minutes before the dragon falls asleep?" It is quite a simple sum, as you see: You could do it in a minute because you have been to a good school and have taken pains with your lessons; but it was quite otherwise with poor Nigel. He sat down to work out his sum with a piece of chalk on a smooth stone. He tried it by practice and the unitary method, by multiplication, and by rule-of-three-and-three-quarters. He tried it by decimals and by compound interest. He tried it by square root and by cube root. He tried it by addition, simple and otherwise, and he tried it by mixed examples in vulgar fractions. But it was all of no use. Then he tried to do the sum by algebra, by simple and by quadratic equations, by trigonometry, by logarithms, and by conic sections. But it would not do. He got an answer every time, it is true, but it was always a different one, and he could not feel sure which answer was right. And just as he was feeling how much more important than anything else it is to be able to do your sums, the Princess came back. And now it was getting dark.