"Oh!" cried Mab, holding fast to the handrail, a little frightened.

"Oh my!" exclaimed Mamma Blake at the top of the cellar steps. "What has happened?"

"Oh my goodness me sakes alive and some orange pudding!" exclaimed Aunt Lolly. "I just knew _something_ would happen!"

But nothing much did, after all, for Daddy Blake, as soon as he heard Hal falling, ran to the foot of the stairs, and there he caught his little boy before Hal had bounced down many steps.

"There you are!" cried Daddy Blake, as he set Hal upright on his feet.

"Not hurt a bit; are you?"

"N-n-n-n-no!" stammered Hal, as he caught his breath, which had almost gotten away from him. "I'm not hurt. Is Roly-Poly?"

Roly was whirling about, barking and trying to catch his tail, so I guess he was not much hurt. The truth was that both Hal and Roly were so fat and plump, that falling down a few cellar steps did not hurt them in the least.

"Well, now we'll look at the burst water pipe," said Daddy Blake, when the excitement was over. The water had stopped spurting out now, though there was quite a puddle of it on the cellar floor by the tubs.

Mr. Blake lifted Hal across this, and showed him where there was a big crack in the water pipe. Then he showed Mab, also lifting her across the little pond in the cellar.

"You see the pipe was full of water," Mr. Blake explained, "and in the night it got so cold down cellar that the water froze, just as it did in the gla.s.s bottle out on the back porch.

"Then the ice swelled up, and it was so strong that it burst the strong iron pipe, splitting it right down the side."

"But why didn't the water spurt out when I came down cellar earlier this morning?" asked Mamma Blake. "It did not leak then."

"I suppose it was still frozen," answered her husband. "But when the furnace fire became hotter it melted the ice in the pipe and that let the water spurt out. But the plumber will soon fix it."

Hal and Mab watched the plumber, to whom their papa telephoned. He had to take out the broken pipe, and put in a new piece. Afterward Hal looked at the pipe that had been split by the ice.

"Why it's just as if gun-powder blew it up," he said, for once he had seen a toy cannon that had burst on Fourth of July, from having too much powder in it.

"Yes, freezing ice is just as strong as gunpowder, only it works more slowly," said Daddy Blake with a smile. "Powder goes off with a puff, a flash and a roar, but ice freezes slowly."

"Oh, but when are we going skating?" asked Mab, as she and her brother started for school, a little later that morning.

"As soon as I can find a frozen pond," said Daddy Blake with a smile.

Well wrapped up, and wearing warm gloves, Hal and Mab went to their lessons. It was so cold that wintry day, though there was no snow, that they ran instead of walking. Running made them warm.

"Is my nose red?" asked Mab, when they were near the school.

"Oh, it's awful red!" cried Hal. "Is mine?"

"As red as a boiled lobster!" laughed Mab. "Let's run faster!"

So they ran, and soon they were in a glow of warmth.

"Oh!" cried Mab, as she and her brother entered the school-yard, "we forgot to ask Daddy why we get warm when we run."

When the two children reached their house, after lessons were over for the day, they found their father waiting for them. He had his skates over his shoulder, dangling from a strap, and he had Hal's and Mab's in his hand.

"Come, we are going to look for the frozen pond!" he said.

Then Hal and Mab forgot all about asking why they became warm when they ran. They cried out joyfully:

"Oh, Daddy is going to take us skating! Daddy is going to take us skating!"

Across the fields they went, and in a little while they came to a place where was a pond, in which they used to fish during the summer.

But now as they looked down on the water, from the top of a small hill, they saw that the pond was all frozen over. A sheet of ice covered it from edge to edge.

"Oh, now we can skate!" cried Hal in delight, "Now we can try our new skates."

CHAPTER V

POOR ROLY-POLY

"Come on!" cried Mab, as she started to run down the slope of the hill toward the frozen pond. "Come on, Hal!"

"Hold on!" called Daddy Blake. "Wait a minute, Mab! Don't go on the ice yet!"

Mab stopped at once. So did Hal, who had just begun to run. You see the children had gotten into the habit of stopping when their uncle called: "Wait a minute and I'll give you a penny," so it was not hard for them to do so when their father called.

"Why can't I go on the ice?" asked Mab,

"I must first see how thick it is," answered Daddy Blake.

"What difference does that make?" Hal wanted to know.

"Oh, a whole lot," said Mr. Blake. "If the ice is too thin you will break through, and go into the cold water. We must be very careful, I will see if it is thick enough."

Mab waited for her father and Hal to come to where she was standing.

Roly-Poly did not wait, however. Down he rushed to the frozen pond.

"Oh, come back! Come back!" cried Mab. "You'll go through the ice, Roly!"

But Roly-Poly paid no attention. Out on the slippery ice he ran, and then he turned around and, looking at Daddy Blake and the two children, he barked as loudly as he could.

Roly-Poly was a queer dog that way. Sometimes he would mind Mab, and then, again, he would not.

"I guess the ice is thick enough to hold up Roly," said Mr. Blake. "It doesn't need to be very strong for that, as Roly is so little."

"How thick must it be to hold us up?" Hal wanted to know.

"Well, on a small pond, ice an inch thick might hold up a little boy or girl," explained Mr. Blake. "But not very many children at a time.

On a large pond the ice should be from six to eight inches thick to hold up a crowd of skaters."