"An ice-boat," remarked Bert. "And going fast, too!"
"Yes, but see! It's coming right toward Flossie and Freddie, and they're skating with their heads down, and don't see it! Oh, Bert! Yell at them! Tell them to look out! Yell at the man in the ice-boat!"
It did indeed seem a time of danger, for a swift ice-boat—one with big white sails and runners, like large skates under it, was skimming over the frozen lake straight for the smaller twins.
CHAPTER II
BUILDING THE "BIRD"
Flossie and Freddie, anxious to win the skating race, were bending over with heads down, as all skaters do who wish to go fast and keep the wind from blowing on them too hard. So they did not see the ice-boat coming toward them, for the craft, blown by the wind, made hardly any noise, and what little it did make was taken up by the clicking of the skates of the smaller twins.
"Oh, Bert! Do something!" cried Nan.
"Yes, yes! I will—of course!"
Bert shook off Nan's hand, for it was still on his arm, and started to skate toward the twins as fast as he could. He hoped to reach them in time to stop them from skating right into the path of the oncoming ice-boat.