"Now, listen," said the astronomer; "we are also under the influence of the earth's centrifugal motion, and wherever we are on the interior surface we swing round our circle of latitude in twenty-four hours, and thus men, ship, and ocean are held up against the interior vault like a boy being able to hold water in a vertical position at the bottom of the pail he swings round him at the end of a cord." "Don't you think, professor," I inquired, "we will become heavier as we approach the region of greatest motion under the equator?" "I don't think so," he replied, "for the ocean around the poles has naturally gravitated to the internal as well as to the external equator, to restore the equilibrium of gravity. The reason why a man does not weigh less on the external equator than at the poles, although flying around at the rate of a thousand miles an hour, is that the deeper ocean, that is, the extra twenty-six miles that the earth is thicker on the equator, counterbalances by its attraction the loss of weight due to the rapid centrifugal motion, and so preserves in all objects on the earth a uniform weight." "The whole thing," said Flathootly, "is as clear as mud. I'm glad to know, sorr, I haven't lost me entire constitution at all evints, an' if I can only carry home what weight I've got lift I'll make a fortune in a dime museum." CHAPTER IX. AFLOAT ON THE INTERIOR OCEAN. As the _Polar King_ sped southward over the interior sea the wonders of the strange world we had discovered began to dawn upon us. The colossal vault rose more and more above us and the sun threw his mild and vertical rays directly upon ship and sea, producing a most delightful climate. The ocean had a temperature of 75 degrees Fahr. and the air 85 degrees. We were absolutely sailing upside down to an inhabitant of the outer sphere, yet we seemed to ourselves to be sailing naturally erect on the sea with the sun above us.