“Whoever may find this, take warning and do not seek to find the north pole.  Danger lurks there.  My name is Andre Christiansen, and I am a Dane, educated in America, who set out to find the pole.  I discovered it but was taken into captivity by the fierce people who dwell around it.  They determined to get rid of me.  With a party I was sent away.  I was to be killed and buried in the ice.  Before they could kill me we were all attacked by polar bears.  All the other men were killed and I was wounded.  As I write this I am dying.  I write it with my blood and a piece of bone.  Send word to Denmark of my death, kind friend whoever you may be that finds this.  If you reach this far in your search for the pole, be warned and go no farther.  This is all I can write.  I am nearly dead.  I put the message in this copper cylinder which I brought along.  I hope it will be found.  Good-bye.”

For a few moments after the professor ceased reading the strange message no one spoke.  They were all thinking of the terrible fate that had befallen Andre Christiansen; to die all alone in that icy land, yet who, in the agony of death had thought to warn some explorer who might come after him.

“Poor fellow,” murmured Amos Henderson.  “He must have died soon after putting the message in the cylinder.”

“And then the bears finished up their work by eating him and the men who wanted to kill him,” said Andy.  “They left only the bones.”

“How long ago do you suppose that was written?” asked Jack.

“There is no telling,” replied the professor.  “But it must have been several years.  I have read of all recent polar expeditions, and within the last twenty years there has been no one of this name to venture toward the pole.  Besides the copper cap on the cylinder has become rusted on, and that would indicate the passage of considerable time.”

“I wonder if there are people at the pole?” came from Mark.

“We’ll go and see!” exclaimed the professor.

“You don’t mean to say you are going further north after what that message says?” asked Andy Sudds.

“Certainly; why not?”

“We may all be killed.”

“We’ll try not to have that happen,” said the professor.  “I am glad you boys found this.  It is a valuable relic,” and Amos Henderson put the message, the trinkets and the cylinder carefully away.

“I—­I guess I won’t go—­” began Andy.

At that instant the airship gave a sudden tremble.  Then the whole craft shivered.  Next it began to rise in the air.

“Here we go!” cried the professor.

CHAPTER XIII

FORWARD ONCE MORE

The airship rose rapidly.  Washington had continued to operate the gas machine until there was a sufficient quantity of vapor to overcome the contracting influence of the cold atmosphere.

“Forward once more!” cried the professor, hurrying to the engine room.  “This time we may reach the north pole!”