They were, indeed, descending the "Hollow Tube" that led to the other side of the world.
"Stop, Hank--stop!" cried the girl; but Hank only uttered a plaintive "Hee-haw!" for it was impossible for him to obey.
After several minutes had passed and no harm had befallen them, Betsy gained courage.

She could see nothing at all, nor could she hear anything except the rush of air past her ears as they plunged downward along the Tube.

Whether she and Hank were alone, or the others were with them, she could not tell.

But had some one been able to take a flash-light photograph of the Tube at that time a most curious picture would have resulted.

There was Tik-Tok, flat upon his back and sliding headforemost down the incline.