"I'll hang it on this nail," said Frank.

"When they looked again Donald said:

"It's fifty-six now."

"How much colder is it than it was in the house?" asked Uncle Robert.

"Twelve degrees," said Frank, counting up the column.

"Oh, let's take it in by the stove," said Susie, "and see how far it will go up."

"What makes you think it will go up by the stove?" asked Uncle Robert.

"Well," answered Susie, "if it goes down when it is cold I should think it would go up when it is warm."

Susie took the little instrument, and, going into the kitchen, held it close to the stove.

"Come," she called, "it is going up already. See!"

"How fast it moves!" said Donald. "Hold it close to the stove, Susie.

Maybe it will go to the very top."

"Let us put it in cold water," said Frank. "It won't hurt the thermometer, will it?"

"Not at all," was the reply. "Try it."

So they held it in the bucket of cold spring water.

"How fast it goes down now!" said Susie. "I wonder if it will go lower than it did out on the porch. It's down to forty-eight."

"Why does Jane set the kettle of cold water on the stove?" asked Uncle Robert, pointing to it.

"To boil the water," answered Susie.

"What makes the water boil?"

"Why, the fire, of course."

"How long will the stove stay hot?"

"As long as there is fire in it."

"Longer than that," said Donald. "It doesn't grow cold the minute the fire is out."

"What becomes of all the heat?" asked Uncle Robert.

"Oh, it goes all round the room."

"Let's put the thermometer in the hot water," said Susie.

"Oh, see it go up!" said Donald. "It is one hundred and fifteen already."

"What is the difference in degrees between the cold and the hot water?"

asked Uncle Robert.

"Sixty-seven degrees," said Frank.

"What makes the difference in degrees?"

"The difference in the heat," said Frank.

"If the water was boiling and the thermometer large enough," said Uncle Robert, "it would go to two hundred and twelve."

"That would be ninety-seven degrees higher," said Frank.

"Wouldn't that be a big thermometer!" exclaimed Susie.

"Now put the thermometer on the floor," said Uncle Robert.

"It's seventy-two degrees now," said Donald in a few minutes.

"Let's put it on the broom," said Susie, "and hold it up to the ceiling."

"It's warmer up there," said Frank, looking at the little gray cylinder when they brought it down. "It is six degrees higher than it was on the floor."

"Why?" asked Uncle Robert.

"The heat must go up there," said Donald.

"It goes into the next room when the door is open," said Frank.

"Does it go outdoors?" asked Uncle Robert.

"Let's open the window and see," said Susie.

Frank opened the window, but, instead of feeling the warm air going out, he felt the cool air coming in.

"Uncle," asked Donald, "isn't the room full of air already?"

"Yes," answered Uncle Robert.

"Then I don't see how any more can come in at the window."

"Are you sure none goes out?"

"I could feel it coming in," said Frank.

"Jane," asked Uncle Robert, "have you a candle?"