“What can we do?” I asked, hiding my perturbation beneath the mask of a low and level voice.
“We may stop here, and die of asphyxiation when our atmosphere tanks are empty,” replied Perry, “or we may continue on with the slight hope that we may later sufficiently deflect the prospector from the vertical to carry us along the arc of a great circle which must eventually return us to the surface. If we succeed in so doing before we reach the higher internal temperature we may even yet survive. There would seem to me to be about one chance in several million that we shall succeed—otherwise we shall die more quickly but no more surely than as though we sat supinely waiting for the torture of a slow and horrible death.”
I glanced at the thermometer. It registered 110 degrees. While we were talking the mighty iron mole had bored its way over a mile into the rock of the earth’s crust.
“Let us continue on, then,” I replied. “It should soon be over at this rate. You never intimated that the speed of this thing would be so high, Perry. Didn’t you know it?”
“No,” he answered. “I could not figure the speed exactly, for I had no instrument for measuring the mighty power of my generator. I reasoned, however, that we should make about five hundred yards an hour.”
“And we are making seven miles an hour,” I concluded for him, as I sat with my eyes upon the distance meter. “How thick is the Earth’s crust, Perry?” I asked.
“There are almost as many conjectures as to that as there are geologists,” was his answer. “One estimates it thirty miles, because the internal heat, increasing at the rate of about one degree to each sixty to seventy feet depth, would be sufficient to fuse the most refractory substances at that distance beneath the surface. Another finds that the phenomena of precession and nutation require that the earth, if not entirely solid, must at least have a shell not less than eight hundred to a thousand miles in thickness. So there you are. You may take your choice.”
“And if it should prove solid?” I asked.
“It will be all the same to us in the end, David,” replied Perry. “At the best our fuel will suffice to carry us but three or four days, while our atmosphere cannot last to exceed three. Neither, then, is sufficient to bear us in safety through eight thousand miles of rock to the antipodes.”
“If the crust is of sufficient thickness we shall come to a final stop between six and seven hundred miles beneath the earth’s surface; but during the last hundred and fifty miles of our journey we shall be corpses. Am I correct?” I asked.