"How are you going to tell?" asked Mab.
"By cutting a little hole through the ice," her father told her. "You can look at the edges of the hole and tell how thick the ice is. We will try it and see."
With the big blade of his knife, Mr. Blake cut and chipped a hole in the ice, a little way from shore. Hal and Mab stayed on the ground watching their father, but Roly-Poly ran all about, barking as hard as he could.
"I guess he is looking for something to bury in a hole," spoke Hal. But Roly could not dig in the hard ice, and the ground was also frozen too solidly for him to scratch. So all the little poodle dog could do was to bark.
"There we are!" cried Mr. Blake, after a bit. "See, children, the ice is more than six inches thick. It will be safe for us to skate on!"
Hal and Mab ran to look into the little hole their father had cut in the ice. It went down for more than half a foot, or six inches, like a well you dig in the sand at the seashore. But no water showed in the bottom of this hole in the ice.
"The ice is good and thick," said Mr. Blake. "It will hold up all the skaters that will come on this pond."
But the children and their Daddy were the only ones there now. Mr. Blake showed Hal and Mab how to put on their skates. He made the straps tight for them, and then put on his own.
"Now we will see how well you can skate," said Mr. Blake.
"I can!" cried Hal. "I've watched the big boys do it. I can skate!"