The following story was taken from this site.
Long ago, there were two brothers, one rich and one poor. The Rich Brother was stingy. It was winter. The wind howled down the chimney, and the snow almost covered the hut in which the Poor Brother lived.
"We cannot starve," said the Poor Brother to his wife. "I will ask my brother to help us."
Now it annoyed the Rich Brother to have the Poor Brother ask for help. When the Poor Brother asked for bread, the Rich Brother said angrily, "Here, take this ham and go to the dwarfs. They will boil it for you."
So the Poor Brother started out, with the ham under his arm, to find the home of the dwarfs. He trudged on through the snow until he saw seven queer little dwarfs rolling a huge snowball, at the foot of a hill.
The dwarfs paid no attention to the Poor Brother, but kept on rolling the snowball, which grew larger and larger each moment, as they sang,
"Behind the door
The Mill you'll find,
But snow, the Mill
Will never grind.
We'll gather snow,
And still more snow,
Then roll it down
To cool Below."
"Ha, ha, ha!" laughed the Chief Dwarf. "We have snow enough here to put out a dozen fires. Come, brothers, let us roll the snowball Below!"
"Heave ho! Heave ho!" cried the other six dwarfs.
In the twinkling of an eye, the seven little dwarfs had rolled the snowball through an entrance in the side of the hill.
Down, down, the snowball rolled, until it reached the place where the fires burned. Then sizzle, sizzle, came the hot steam pouring out of the entrance.
All this time the Poor Brother had stood watching the seven dwarfs, and saying not a word. But suddenly he thought, "If I do not go Below at once, there will be no fire left to boil my ham."
So the Poor Brother groped his way through the steam and the smoke, and at last he found his way into the home of the seven dwarfs.
It certainly was a very queer place! There were great fires burning on every side. Although the huge snowball had cooled the air, it had not quenched the fires.
The Chief Dwarf was stirring some fat that was boiling in a kettle. When he saw the Poor Brother standing before him with the ham under his arm, he cried, "Ho, ho! Who comes here?"
Before the Poor Brother could answer, the seven little dwarfs had crowded around him, teasing for the ham. It was many a day since they had tasted ham, and they were very fond of it.
"What will you give me for the ham?" asked the Poor Brother.
"We have neither silver nor gold," said the dwarfs, "but we will give you the Mill that stands behind the door."
"Of what use would the Mill be to me? I am hungry and have come to boil the ham," said the Poor Brother.
"It is a wonderful Mill," the Chief Dwarf replied. "It will grind anything in the world that you might wish, excepting snow and ham. I will show you how to use it."
The Poor Brother agreed to give the ham in exchange for the Mill, and the Chief Dwarf told him how to use it.
The dwarf said, "When you wish the Mill to grind, use these words: Grind, quickly grind, little Mill, Grind--with a right good will! When you wish the Mill to stop grinding, you must say, Halt, halt, little Mill!
The Mill will obey you."
Taking the little Mill under his arm, the Poor Brother climbed up and up, until he came to the entrance in the side of the hill. Then he trudged home again through the snow.
When he arrived in front of the hut, he put the little Mill down on the snow, and said at once, "Grind, quickly grind, little Mill, Grind a HOUSE--with a right good will!"
The little Mill ground and ground, until there stood, in place of the hut, the finest house in the world. It had fine large windows and broad stairways, and the house was furnished from garret to cellar.
By spring, the Mill had ground out the last article that was needed for the house, and the Poor Brother cried, "Halt, halt, little Mill!" The Mill obeyed him.
Then the Poor Brother placed the Mill in the barnyard and told it to grind horses, cows, woolly sheep, and fat little pigs.
When he told it to halt, the Mill stopped grinding.
The Poor Brother carried the Mill to the fields and commanded it to grind rich crops of wheat, oats, barley, and corn.
Then he took the Mill into the house and asked it to grind fine clothing for his wife and his daughters, and to keep all the cupboards filled with good things to eat.
At last the Poor Brother had everything that he wanted. He placed the Mill behind the kitchen door and sat down, with his wife and daughters, to eat the choicest food he had ever tasted.
The Rich Brother heard about all the strange things that had happened, and he went to visit the Poor Brother.
"How did you manage to become so rich?" he asked in astonishment.
The Poor Brother told about the Mill, and that he need only say,
"Grind, quickly grind, little Mill, Grind--with a right good will!" And the Mill would grind anything he might wish to have.
The Rich Brother did not wait to hear any more but said, "Lend the Mill to me for an hour."
Taking it under his arm, the stingy Rich Brother ran across the fields toward home.
His wife was in the hayfield, spreading the hay after the mowers. He passed her on the way home and told her that he would attend to breakfast that morning.
"I will call you when all is ready," said he.
When the Rich Brother reached home, he placed the Mill on the table, and told it to grind porridge and red herrings.
The Mill began at once to grind oatmeal porridge and fat red herrings.
All the dishes and pans were soon filled. Then the porridge and herrings began to flow over the kitchen floor into the yard.
The Rich Brother tried to stop the Mill. He turned and twisted and screwed the handle, but he could not stop it, for he did not know the magic words.
At last he waded through the porridge across the fields to the mowers, crying, "Help! Help!"
When he told the mowers about the Mill, they said, "Ask your brother to stop the Mill, or we shall be drowned in porridge."
Then the Rich Brother ran to the Poor Brother's house, crying and shouting for help.
The Poor Brother laughed when he found out what had happened. They rowed back to the kitchen in a boat, and the Poor Brother whispered the magic words. The Mill stopped grinding.
In the course of time, the porridge soaked into the ground, but after that nothing would grow there excepting oats, and afterwards the brooks and ponds were always filled with herrings.
The Rich Brother no longer wished to keep the Mill. The Poor Brother carried it home once more and placed it behind the door.
Years afterwards, a rich merchant sailed from a distant land and anchored his ship in the harbor. He visited the home of the Poor Brother and asked about the Mill, for he had heard how wonderful it was.
"Will it grind salt?" the merchant asked.
"Yes, indeed!" said the Poor Brother. "It will grind anything in the whole world excepting snow and ham."
"Let me borrow the Mill for a short time, and great will be your reward," said the merchant.
He thought it would be much easier to fill his ship with salt from the Mill, than to make a long voyage across the ocean to procure his cargo.
The Poor Brother consented gladly. The merchant went away with the Mill. He did not wait to find out how to stop the grinding.
When the merchant went aboard the ship, he said to the captain, "Here is a great treasure. Guard it carefully."
The captain thought that the little Mill did not appear very wonderful, but he placed it upon the deck of the ship. Then he ordered the sailors to their posts of duty, and the ship sailed away.
When they were out at sea, the merchant said, "Captain, we need not go any further upon our voyage. The Mill will grind out salt enough to fill the hold of the ship." So saying he cried, "Grind, quickly grind, little Mill, Grind SALT--with a right good will!" And the Mill ground salt, and more salt, and still more salt. When the hold of the ship was full of salt, the merchant cried, "Now you must stop, little Mill."
But the little Mill did not stop. It kept on grinding salt, and more salt, and still more salt.
The captain shouted, "We shall be lost! The ship will sink!"
One of the sailors called, "Ahoy, captain! Throw the Mill overboard."
So, heave ho! Heave ho! And overboard went the wonderful Mill, down to the bottom of the deep sea.
The captain and his crew sailed home with the merchant's cargo of salt.
But the Mill kept on grinding salt at the bottom of the sea.
AND THAT IS WHY THE SEA IS SALT.
At least, so some people say.