Considerable space in the Snowbird was occupied by Professor Henderson's scientific instruments. He was amply supplied with powerful field glasses, a wonderful telescope, partly of his own invention; instruments for the measuring of mountains heights, the recording of seismic disturbances, and many other scientific paraphernalia of which Jack and Mark did not know even the uses.

The boys were as well supplied with firearms as Andy Sudds himself. They knew that they would probably see and be obliged to kill dangerous beasts; and although the several tribes of Indians inhabiting Alaska are all supposed to be semi-civilized and at peace with the whites, they had had experience enough in wild countries before to warn them that the temper of aboriginal man is never to be trusted too far.

Their own readiness for departure in the Snowbird had been gauged by the telegraph dispatches from Fort Yukon. When the final message came that the boat bearing the supplies had started, Professor Henderson asked: "And now, boys, when can we leave by the air route?"

Jack and Mark glanced at each other and nodded. Jack said:

"All you have to do, Professor, is to put your bag aboard the ship and step in. We are ready to start the Snowbird at any moment. Andy has his guns aboard, and plenty of ammunition. Mark and I are all ready. At your word we will leave."

"It is already dark," said the professor, slowly. "Shall we wait until morning?"

"The moon will be up in an hour—and it is almost at its full," Mark said, quickly. "The quicker we are off the better, it seems to me."

"Very well," agreed Professor Henderson. "If you boys say the word, we will start. Is Andy here?"

"He is already aboard—asleep in his bunk," said Jack, "with his best rifle cuddled in the hollow of his arm. He does not propose to be left behind," and the young fellow chuckled.

"And where is Washington White?"