"It's awful cold outside," said Jack, shivering from the remembrance.
Without a word the professor, wrapping a dressing-gown about him, hurried to the engine room, where several thermometers were kept. One was outside, and could be read through a glass side.
"No wonder you felt cold," he said to Jack, when he returned. "It's ten degrees below zero!"
The boys hurried to complete their dressing. The professor did likewise, as he was anxious to take some observations.
"Get out the fur garments," he said. "We must take no more chances now. It will become colder rapidly, and ordinary clothes will be of no protection."
The boys and the professor donned heavy fur coats, with immense gloves and caps that covered all of their faces but the eyes. Then they went outside. Jack was the first to look over the side of the ship. As he did so he uttered a cry of astonishment.
Down below, about three-quarters of a mile, was a great white, snowy waste. Giant mountains of ice were heaped on every side. It was a cold, frosty silent world that the Monarch was flying over. They had reached the frozen north! They were at the beginning of the entrance to the land of the Pole!
CHAPTER X
LOST IN AN ICE CAVE
"I'm not surprised that the thermometer is down below zero," remarked
Jack. "There's enough ice under us to supply the whole United States."