The Story Book of Science  by Jean Henri Fabre

The Wily Dervish

"T HERE are ant-hills everywhere, large or small," observed Jules. "Even in the garden I could have counted a dozen. From some the ants are so numerous they blacken the road when they come out. It must take a great many plant-lice to nourish all that little colony."

"Numerous though they be," his uncle assured him, "they will never lack cows, as plant-lice are still more numerous. There are so many that they often seriously menace our harvests. The miserable louse declares war against us. To understand it, listen to this story:

"There was once a king of India who was much bored. To entertain him, a dervish invented the game of chess. You do not know this game. Well, on a board something like a checkerboard two adversaries range, in battle array, one white, the other black, pieces of different values: pawns, knights, bishops, castles, queen and king. The action begins. The pawns, simple foot-soldiers, are destined as always to receive the first of the glory on the battlefield. The king looks on at their extermination, guarded by his grandeur far from the fray. Now the cavalry charge, slashing with their swords right and left; even the bishops fight with hot-headed enthusiasm, and the ambulating castles go here and there, protecting the flanks of the army. Victory is decided. Of the blacks, the queen is a prisoner; the king has lost his castles; one knight and one bishop do wonderful deeds to procure his flight. They succumb. The king is checkmated. The game is lost.

Chess-board with Pieces   in Position

"This clever game, image of war, pleased the bored king very much, and he asked the dervish what reward he desired for his invention.

" 'Light of the faithful,' answered the inventor, 'a poor dervish is easily satisfied. You shall give me one grain of wheat for the first square of the chessboard, two for the second, four for the third, eight for the fourth, and you will double thus the number of grains, to the last square, which is the sixty-fourth. I shall be satisfied with that. My blue pigeons will have enough grain for some days.'

" 'This man is a fool,' said the king to himself; 'he might have had great riches and he asks me for a few handfuls of wheat.' Then, turning to his minister:—'Count out ten purses of a thousand sequins for this man, and have a sack of wheat given him. He will have a hundred times the amount of grain he asks of me.'

" 'Commander of the faithful,' answered the dervish, 'keep the purses of sequins, useless to my blue pigeons, and give me the wheat as I wish.'

" 'Very well. Instead of one sack, you shall have a hundred.'

" 'It is not enough, Sun of Justice.'

" 'You shall have a thousand.'

" 'Not enough, Terror of the unfaithful. The squares of my chessboard would not have their proper amount.'

"In the meantime the courtiers whispered among themselves, astonished at the singular pretensions of the dervish, who, in the contents of a thousand sacks, would not find his grain of wheat doubled sixty-four times. Out of patience, the king convoked the learned men to hold a meeting and calculate the grains of wheat demanded. The dervish smiled maliciously in his beard, and modestly moved aside while awaiting the end of the calculation.

"And behold, under the pen of the calculators, the figure grew larger and larger. The work finished, the head one rose.

" 'Sublime Commander,' said he, 'arithmetic has decided. To satisfy the dervish's demand, there is not enough wheat in your granaries. There is not enough in the town, in the kingdom, or in the whole world. For the quantity of grain demanded, the whole earth, sea and continents together, would be covered with a continuous bed to the depth of a finger.'

"The king angrily bit his mustache and, unable to count out to him his grains of wheat, named the inventor of chess prime vizier. That is what the wily dervish wanted."

"Like the king, I should have fallen into the dervish's snare," said Jules. "I should have thought that doubling a grain sixty-four times would only give a few handfuls of wheat."

"Henceforth," returned Uncle Paul, "you will know that a number, even very small, when multiplied a number of times by the same figure, is like a snow-ball which grows in rolling, and soon becomes an enormous ball which all our efforts cannot move."

"Your dervish was very crafty," remarked Emile. "He modestly contented himself with one grain of wheat for his blue pigeons, on condition that they doubled the number on each square. Apparently, he asked next to nothing; in reality, he asked more than the king possessed. What is a dervish, Uncle?"

"In the religions of the East they call by that name those who renounce the world to give themselves up to prayer and contemplation."

"You say the king made him prime vizier. Is that a high office?"

"Prime vizier means prime minister. The dervish then became the greatest dignitary of the State, after the king."

"I am no longer surprised that he refused the ten purses of a thousand sequins. He was waiting for something better. The ten purses, however, would make a good sum?"

"A sequin is a gold piece worth about twelve francs. At that rate, the king offered the dervish a sum of one hundred and twenty thousand francs, besides the sacks of wheat."

"And the dervish preferred the grain sixty-four times doubled."

"In comparison what was offered him was nothing."

"And the plant-lice?" asked Jules.

"The story of the dervish is bringing us to that directly," his uncle assured him.