sea. If the densities of the atmosphere decrease in a geometrical as the distances from sea-level increase in an arithmetical ratio, then, at a distance of only one hundred miles up, we should have virtually a perfect vacuum. The rarity there would be absolutely inconceivable. For the atmospheric density at that height would be only one billionth of. what it is at the earth 's surface.
"And what is the real density there?"
"No man knows or can know," replied Rhodes, "until he goes up there to see. But meteors, rendered incandescent by the resistance they, encounter, show that a state of things exists at that high altitude very different from the one that would be found there if our formulae were correct and our theories were valid. And so, I have no doubt, we shall find it down in Drome.
"Formulæ are very well in their place," he went on, "but we should never forget, Bill, that they are often budded on mere assumption and that a theory is only a theory until experiment (or experience) has shown us that it is a fact. And that reminds me: do you know what Percival Lowell says about formulæ?"
I said I didn't.
"'Formulæ,' says. the great astronomer, 'are the anesthetics of thought.' I commend that very highly," Milton added, "to our fiction editors and our writers of short stories."
"But"
"But me no buts, Bill," said Milton. "And w r hat do your scientists know about the interior of this old earth we inhabit, anyway? Forsooth, but very little, Billy me lad. Why, they don't even know what a volcano is. One can't make a journey into the interior of the earth on a scratchpad and' a lead-pencil, or if he does, we may be pardoned if we do not give implicit credence to all that he chooses to tell, us when he comes back. For instance, one of these armchair Columbuses (he made the journey in a machine called d2y by dx2 and came out in China) says that he found the interior in a state of igneous fluidity. And another? Why, he tells us that the whole earth is as rigid as steel, that it is solid to the very core."
"It seems," said I, "to be a case of
"'Great contest follows, and much learned dust
Involves the combatants; each claiming truth,
And truth disclaiming both.'"
"The truth in this case is not yet known," replied Rhodes, "though I trust that you and I, Bill, are fated to learn it."
He smiled a queer, wan smile.
"Whether we are fated, also, to re-veal it to the" world, our world—well, quién sabe?" said Milton Rhodes.
"Then," I remarked, my fingers busy removing my ice-creepers, "what we read about the state of things in the interior of the earth—the temperature, the pressure, the density—then all that is pure theory?"
"Of course. How could it be any-thing else? All theory, save, that is, the mean density of the, earth. And that mean density gives us something to think about, for it is just a little more than twice that, of the surface materials. With all this enormous pressure that we hear so much about and the resultant increase of density with depth, the weight of the earth certainly ought to be more than only five and one-half time's that of a globe of equal" size composed of nothing but water."
"Kind of queer, all right," was my comment.
"It is queer, all right—as the old lady said when she kissed the cow. However, as old Dante has it, 'Son! our time asks thriftier using.'"
As the last, word left his lips, I straightened up, the toothed shoes in
