This is what Phineas said she said, but when next I met her she told me that he had declared that if I had put the well where he thought it ought to be, I should have been having all the water I wanted before now. My optimist was dreadfully cast down when he heard that I would drive no deeper. "I have been afraid of this," he said. "I have, been afraid of it. And if circumstances had so arranged themselves that I should have command of money, I should have been glad to assume the expense of deeper explorations. I have been thinking a great deal about the matter, and I feel quite sure that even if you did not get water or anything else that might prove of value to you, it would be a great advantage to have a pipe sunk into the earth to the depth of, say, one thousand feet." "What possible advantage could that be?" I asked. "I will tell you," he said. "You would then have one of the grandest opportunities ever offered to man of constructing a gravity-engine. This would be an engine which would be of no expense at all to run. It would need no fuel. Gravity would be the power. It would work a pump splendidly. You could start it when you liked and stop it when you liked." "Pump!" said I. "What is the good of a pump without water?" "Oh, of course you would have to have water," he answered. "But, no matter how you get it, you will have to pump it up to your tank so as to make it circulate over your house. Now, my gravity-pump would do this beautifully. You see, the pump would be arranged with cog-wheels and all that sort of thing, and the power would be supplied by a weight, which would be a cylinder of lead or iron, fastened to a rope and run down inside your pipe. Just think of it! It would run down a thousand feet, and where is there anything worked by weight that has such a fall as that?" I laughed. "That is all very well," said I. "But how about the power required to wind that weight up again when it got to the bottom? I should have to have an engine to do that."