[Ill.u.s.tration: The coming storm.]

They reached the porch just as it began to fall thick and fast. A moment more and it came down in floods, while at the same time the darkness pa.s.sed away.

"How cool it is growing!" said Mrs. Leonard.

"It is twelve degrees cooler than it was at noon," said Donald, looking at the thermometer. "See, the wind has changed. It is from the northeast now."

Frank went into the dining-room, and when he came back he said, "The barometer has risen two-tenths of an inch since we looked at it last."

It seemed to rain harder than ever. The water was driven in sheets before the strong northeast wind. A stream began to run down the garden path. A vivid flash of lightning was followed quickly by a loud crash of thunder.

"That struck somewhere near," said Frank.

"I believe it was over in the wood," said Mrs. Leonard.

"See," said Uncle Robert in a few moments, pointing to a line of light in the western sky, "it is clearing already. The shower will soon be over."

The light in the west grew rapidly. The lightning became less frequent.

The thunder rolled farther and farther away. The rain fell less and less heavily. The weather vane that had pointed to the northeast began to waver, and then turned toward the southwest again. It rained steadily but more gently as the clouds rolled away eastward.

And then the sun, lower now by two hours than when it was first hidden by the cloud, shone out clear and bright. Instantly everything glistened as with millions of diamonds. Even the air seemed to be filled with them, as though each raindrop was turned into a jewel as it fell.

Uncle Robert went to the front of the house and looked toward the dark cloud that was now piled up in the eastern sky.

"Come and see the rainbow!" he called.

As they looked at the bright and perfect arch that lay against the dark ma.s.s of clouds, Susie asked, "What makes rainbows, uncle?"

"It is the sun shining on the rain," replied Uncle Robert "This beautiful sunlight is made up of many, many rays. These rays fly from the sun as straight as arrows from a bow, unless something comes in their way to stop them. It seems as though such sharp little arrows of light would go right through raindrops. But they don't. They glance off the little round b.a.l.l.s of water and bound up again like rubber b.a.l.l.s.

"Now you know if you throw a ball straight down at your feet it bounds back into your hands. If you throw it from you, when it strikes the ground it bounds farther away. It is just so with these little arrows of light that we call rays. If the sun is high, as it is at noon, the rays are thrown back to it again. That is why we never have rainbows at noon.

But when the sun is low, as it is now, instead of going back to the place they came from, they bound up against that cloud, and so make the wonderful rainbow."

"But, uncle," asked Donald, "why do we see so many colors in the rainbow? They are not in the sunlight."

"Oh, yes, they are," was the answer. "These rays of light are of the same colors that we see in the rainbow. It takes all of them mixed together to make the clear white light which we call sunlight, and without which nothing could live or grow.

"As the raindrops throw them up against that cloud, they are separated again, because some colors are more easily bent than others. The red, you see, is the highest and the violet the lowest in the bow. The raindrops make a prism. You have seen a prism. But through the prism the colors are turned the other way; the red is lowest and the violet highest."

"How fast the rainbow is fading away!" said Susie. "I wish it would stay."

"The rain is over," announced Donald, leaving them and walking out toward the garden. "The sky is quite clear."

"It is getting warm again," said Frank, looking at the thermometer, "but it does not feel hot as it did before the rain."

"The barometer is just where it was this morning," said Susie, coming from the dining-room.

"It is drying off very fast," said Uncle Robert. "Let us walk out and see how the garden stood its drenching."

"Put on your rubbers, Susie," called Mrs. Leonard from the house.

As they crossed the yard they pa.s.sed a pan in the bottom of which the water stood an inch or more deep.

"That shows how much rain fell," said Uncle Robert, pointing to the pan.

"Do you mean if it had stayed on the ground where it fell it would have been that deep all over?" asked Susie. "Would that have been very much?"

"I think it would," was the smiling reply. "You might try to find out how much fell on the garden alone if it was an inch deep all over."

Susie shook her head.

"I don't know how," she said.

"Uncle," said Frank, "in the weather reports they always tell how much rain falls, even if it is only a small part of an inch. How can they tell when it is so little?"

"They have what is called a rain gauge, by which a very small amount of rainfall can be measured. By the way, we might have a rain-gauge of our own. It would be easy to make one with the help of a tinsmith. Is there a tinsmith in the village?"

"Yes," answered Frank, "but I don't believe he has much to do."

"So much the better for us," laughed Uncle Robert. "Susie, while these other people are busy tomorrow, shall we drive to the village and see if we can get the tinsmith to help us make a rain-gauge? I have a little book somewhere that tells just how it should be done."

Susie was delighted at the thought of such a day with Uncle Robert, and the boys were so interested in the prospect of having a rain-gauge of their own that they could hardly wait for to-morrow to come.

CHAPTER XI.

THE VILLAGE.

The next morning Frank harnessed Nell for Uncle Robert and Susie to drive into the village to see the tinsmith.

It was a delightful ride through the woods and the fields washed clean by the rain. The birds were singing gayly. The air was fresh and clear.

Long shadows lay along the road.

The tinsmith was sitting by his open door, tilted back in an old wooden chair. As Nell stopped, he brought his chair down on its four legs and said:

"Good morning."

Uncle Robert lifted Susie out of the wagon and hitched Nell to a post.

The tinsmith rose to his feet, smiling to Susie, who said:

"This is my Uncle Robert, Mr. Mills. We've come to have a rain-gauge made."

"Good morning," said Uncle Robert, turning to Mr. Mills, who looked as if he thought rain gauges were not exactly in his line. "Can you spare us a little time this morning? Susie must have her rain-gauge before the next shower."

"Come right in," said Mr. Mills, "and tell me what your rain-gauge looks like. I never heard of such a thing."