But it never came. Suddenly as they stood there, tense and waiting, a terrific convulsion shook the earth. With a terrible roar the great cavern collapsed and a vast burst of smoke and flame vomited to the sky, and a deep crater was left by the subsidence. Sick and dizzy, with showers of stones falling all around them, they stood aghast while explosion after explosion rent the air, rendering the crater deeper. It was some minutes before quiet reigned again and, white and shaken, after their nerve-racking experience, they were able to collect their shaken faculties and make an examination of the scene.
The hill beneath which the cavern was located had practically disappeared; in its place was left nothing but a heap of torn and tumbled earth and rock. Its dreadful secret was safe, for the cave and its contents, and the men who had wielded such titanic forces, were buried deep under tens of thousands of tons of débris.
Perhaps it was as well, Dick thought. There are some forms of knowledge which mortals ought not to possess; there are some powers which they are not fit to handle.
Whatever secret Gronvold had discovered, it rested with him for ever on the very scene of his ill-omened labours. What had gone wrong in the depths of the cavern they could not even imagine, but it was evident that the mysterious force which Gronvold had called into existence, whatever it was, had destroyed him and his companions. And it was almost by a miracle that Dick, Yvette, and Jules had escaped.
Slowly and painfully they made their way back to their camp, and for the first time Dick became conscious of the great weight of the double handful of shot which he had taken from the tank. He drew some of it out and examined it by the light of the fire. As he did so he gave a cry of surprise. For the “shot” was nothing more or less than tiny nuggets of virgin gold.
Here was an addition to the mystery. As Dick knew perfectly well, there was not an atom of gold-bearing rock within hundreds of miles of where they stood.
It was evident that one of the secrets of Gronvold’s invention was that it gave him the power of actually bringing about the transmutation of substances. There was some element in the rock which was susceptible of being changed into gold by a process at which they could not even guess. But if this were so, Gronvold had indeed, as they suspected, been able to solve the problem of loosing the incredible force contained in the atom. His discovery was, as Dick at once realised, on the lines of the latest development of scientific thought.
Dick was to see the problem solved in later years by more reputable investigators.
But he could never forget his strange encounter with the wonderful but misguided genius whose career had been so terribly brought to an end by the dread power he had himself evoked.