Uncle Robert's Geography (Uncle Robert's Visit, V.3) by Helm, Nellie Lathrop, Parker, Francis W., 1837-1902

"What difference would that make?" asked Susie.

"Look at the woodpile out there," said her uncle. "Where do you think the weight of the wood would be the greater? On the ground or halfway to the top?"

"On the ground, of course," answered Susie.

"Well, they found it was the same with the air. As they went up the mountain the mercury in the tube fell."

"That showed that the weight on it was less, didn't it, uncle?" said Frank. "I think that was a very wonderful discovery, don't you?"

"It was, indeed," replied Uncle Robert, "and that is how the first barometer was made."

[Illustration: Barometer.]

"Is that what a barometer is?" asked Donald.

"Yes," was the reply, "simply a glass tube about thirty-three or thirty-four inches long, closed at the top, and filled with mercury. It is then placed in a small open cup, called the cistern, into which the mercury flows until the air pressing on it there will let it fall no farther."

"Does it always stay at the same height in the tube?" asked Donald.

"Oh, no," his uncle answered. "Some days the air is heavier than others, and so presses harder on the mercury."

"That would make it rise, wouldn't it?" asked Susie.

"Yes, dear."

"So, uncle," said Frank, taking up the Weather Report, "where it says 'High' here, it means that the air is heavier than where it says 'Low.' Is that it?"

"That's right," replied Uncle Robert; "and when the barometer is low we know there will be a storm."

"Well"--and Donald stood up and stretched himself--"I wish I could see a barometer."

"You shall," said Uncle Robert "I will send for one. You may carry the letter to the post office to-morrow when you go for the mail."

CHAPTER VIII.

A WALK IN THE WOODS.

It was a beautiful Sunday afternoon. The sun had marked its shortest shadows. They were now pointing toward the northeast.

The family had returned from the little village church. Dinner was over, and they had all gone into the cool, shady piazza. Mrs. Leonard and Susie had settled themselves cozily in one corner and were reading together. Mr. Leonard was nodding over the pages of his weekly newspaper. Frank, stretched out on the settee, was absorbed in a new book, while not far away Donald lay under the spreading branches of a spruce tree with Barri by his side. Uncle Robert stood gazing at the green woods, which looked so cool and inviting.

"'The groves were God's first temples,'" he said to himself, and then, turning to the others, asked, "Who wants to go for a walk?"

"I do," said Frank, springing up. "Come on, Don. Don-ald!" he called, "we're going for a walk."

"You'd better come with us," said Uncle Robert to Mrs. Leonard.

"I'll get your hat, mother," cried Susie eagerly, running into the house.

"Shall we go to the cornfield?" asked Mr. Leonard, picking up his straw hat.

"I think it would be cooler in the woods," said Mrs. Leonard.

"Oh, yes," said Donald, "let's go up the creek to the pond."

The country was in the full glory of early summer. Just beyond the rich green of the great cornfield could be seen the peaceful river. The yellowing grain on the upland waved gently in the breeze. Under the wide-spreading oak trees in the pasture the cows were lazily chewing their cuds. A feeling of quiet pleasure filled the air.