When I first met Professor Hancock his apparatus was rather primitive, but he was able to show me the distribution of rock down to a depth of several hundred feet and we could see quite clearly a part of the Bakerloo Line which passed very near his laboratory. Much of the Professor’s success was due to the great intensity of his supersonic bursts; almost from the beginning he was able to generate peak powers of several hundred kilowatts, nearly all of which was radiated into the ground. It was unsafe to remain near the transmitter, and I noticed that the soil became quite warm around it. I was rather surprised to see large numbers of birds in the vicinity, but soon discovered that they were attracted by the hundreds of dead worms lying on the ground.
At the time of Dr Clayton’s death in 1960, the equipment was working at a power level of over a megawatt and quite good pictures of strata a mile down could be obtained. Dr Clayton had correlated the results with known geographical surveys, and had proved beyond doubt the value of the information obtained.
Dr Clayton’s death in a motor accident was a great tragedy. He had always exerted a stabilizing influence on the Professor, who had never been much interested in the practical applications of his work. Soon afterwards I noticed a distinct change in the Professor’s outlook, and a few months later he confided his new ambitions to me. I had been trying to persuade him to publish his results (he had already spent over £50,000 and the Public Accounts Committee was being difficult again), but he asked for a little more time. I think I can best explain his attitude by his own words, which I remember very vividly, for they were expressed with peculiar emphasis.
“Have you ever wondered,” he said, “what the Earth really is like inside? We’ve only scratched the surface with our mines and wells. What lies beneath is as unknown as the other side of the Moon.
“We know that the Earth is unnaturally dense—far denser than the rocks and soil of its crust would indicate. The core may be solid metal, but until now there’s been no way of telling. Even ten miles down the pressure must be thirty tons or more to the square inch and the temperature several hundred degrees. What it’s like at the centre staggers the imagination: the pressure must be thousand of tons to the square inch. It’s strange to think that in two or three years we may have reached the Moon, but when we’ve got to the stars we’ll still be no nearer that inferno four thousand miles beneath our feet.
“I can now get recognizable echoes from two miles down, but I hope to step up the transmitter to ten megawatts in a few months. With that power, I believe the range will be increased to ten miles; and I don’t mean to stop there.”
I was impressed, but at the same time I felt a little sceptical.
“That’s all very well,” I said, “but surely the deeper you go the less there’ll be to see. The pressure will make any cavities impossible, and after a few miles there will simply be a homogeneous mass getting denser and denser.”
“Quite likely,” agreed the Professor. “But I can still learn a lot from the transmission characteristics. Anyway, we’ll see when we get there!”
That was four months ago; and yesterday I saw the result of that research. When I answered his invitation the Professor was clearly excited, but he gave me no hint of what, if anything, he had discovered. He showed me his improved equipment and raised the new receiver from its bath. The sensitivity of the pickups had been greatly improved, and this alone had effectively doubled the range, altogether apart from the increased transmitter power. It was strange to watch the steel framework slowly turning and to realize that it was exploring regions, which, in spite of their nearness, man might never reach.