Uncle George had taught his little friends many things from what he called the Book of Nature, and what they had learnt made them eager to know more.

One day as Dolly, the boys, and Uncle George were in the garden they saw that a tulip, which the day before was in full bloom and strong, was now lying dead on the ground.

“Poor little tulip!” said Dolly. Both the boys were sorry too. They had watched it come through the ground like a blade of grass, open out its bud, and expand its bloom. Now all was over. The little flower would no longer enjoy the bright sunshine or the rain. It would no longer send forth its rootlets in search of the food it so much liked.

“Have you ever thought, Dolly, how the tulip, and indeed all plants, take their food from the soil?” asked Uncle George.

“I know they must feed in some way,” said Dolly, “or they would not grow. But I do not know how they do it.”

“Should you like to know, Dolly?” asked Uncle George.

“Indeed I should,” said the little girl.

The boys were just as eager as Dolly to know about this, so Uncle George and the children went indoors for a lesson.

“I cannot tell you how plants take their food from the soil without first of all showing you what happens when water and soil are mixed together in a tumbler,” said Uncle George. “Tom will fetch me a tumbler, and you, Frank, bring me a little water.”

When these were brought, Uncle George put a spoonful of soil into the tumbler, and then poured some water on it.

“Stir it up, please, Dolly,” said Uncle George, “and you may pretend you are going to make a pudding.”

Dolly did so.

“Now let us put it aside for a few minutes, while we place the flowers we have gathered into the vases,” said Uncle George. “Then we will look at our tumbler of muddy water.”

How pretty the flowers were made to look! How fresh they were! and how pleasant was their scent! The children hardly thought of the tumbler, but Uncle George was ready now for the lesson.

“Look! look, at the tumbler,” said he. “Do you see a change?”

“Indeed we do,” said all the children in one voice.

“The mud has sunk to the bottom of the glass,” added Tom, “and the water on the top is clear.”

Uncle George poured some of the clear water into a clean flat dish. Then he took a spirit-lamp from a little cabinet, and heated the water in the dish with it.

The children watched to see what would happen. Soon a cloud was seen over the dish, and by and by all the water had gone.

“But what is that at the bottom of the dish?” asked Uncle George.

“It looks like powder,” said Frank.

“And it must have been in the water all the time,” added Tom.

“And yet the water was clear,” said Uncle George. “Look once more.”

As he spoke, Uncle George took a glass of clean water from the tap. He put two large spoonfuls of salt in, and stirred it up.

“You see,” he said, “the salt has gone from sight. Still the water is clear. Where has it gone?”

“Into the water,” said Tom.

Uncle George put more salt in the water, and stirred it up. He kept on doing this until the water would take up no more salt, no matter how much it was stirred. This he called brine.

“Now, Frank, please go and ask mother for a fresh egg,” he said, “and you, Tom, please bring me some fresh water in another glass.”

Uncle George placed the egg in the glass in which the salt had been put, and it floated in it. He then placed the egg in the glass of fresh water, and it at once sank to the bottom.

“Can you explain this!” he said.

“The salt water is heavier and thicker than the fresh water. That is why it bears up the egg,” said Frank.

“That is very good indeed, Frank. That is just the reason. The salt water or brine is denser, or heavier, than the other.”

Uncle George next took a glass tube with a thistle-shaped bulb at the end of it. Frank kept his finger on the small end, while his uncle poured some of the brine into the bulb. He next tied a piece of bladder skin over the bulb, and placed it in a glass of fresh water, so that the salt water in the tube was at the same level as the fresh water in the glass.

Then he took two small glass bottles. He filled one with fresh water and the other with brine, and tied a piece of bladder skin over the mouth of each. The one which was filled with brine he placed in a larger dish of fresh water. The other, that is the one filled with fresh water, he placed in a dish of brine.

“Now, children, we will go and have tea,” he said, “and when we come back we will see if any change has taken place.”

About an hour later Uncle George, Dolly, and the boys came back.

“Oh,” said Frank, “look, Uncle George! The water has risen up in the thistle tube.”

“Yes, how do you account for that, Frank?”

“Some of the fresh water has passed through the skin,” Frank answered.

“Now taste the water in the glass outside the skin,” said Uncle George. “It was fresh water when we put it in, wasn’t it?”

Frank did so. Tom tasted it too. Both boys declared that it was now salt.

“Where did the salt taste come from?” their uncle asked.