Mesmer at this date was a youth of twenty-four, but the writings of Van Helmont and Wirdig and G. Maxwell had already thrown more than a glimmering of light upon the reciprocal action of bodies upon each other, and had already demonstrated the existence of a universal magnetic force by which the human will was rendered capable of influencing the minds of others. It was not, however, till seventeen years later--in the year 1775, to be precise--that Mesmer published his famous letter to the Academies of Europe. And by a strange chance it was in the same year that I secured a further confirmation of his doctrines and at the same time an explanation of the one matter concerned with this history of which I was still in ignorance. In a word, I learned at last how young Peter Tortue came by his death. I did not learn it from his father. That implacable man I never saw after the night when we listened to his footsteps descending the stairs in the darkness. He was gone the next morning from the islands, nor was any trace of him, for all the hue and cry, discovered for a long while--not, indeed, for ten years, when my son, who was then a lad of eight, while playing one day among the rocks of Peninnis Head on St. Mary's, dropped clean out of my sight, or rather out of Helen's sight, for I was deep in a book, and did not raise my head until a cry from my wife startled me. We ran to the loose pile of boulders where the boy had vanished, and searched and called for a few minutes without any answer. But in the end a voice answered us, and from beneath our feet. It was the boy's voice sure enough, but it sounded hollow, as though it came from the bowels of the earth. By following the sound we discovered at last between the great boulders an interstice, which would just allow a man to slip below ground. This slit went down perpendicularly for perhaps fifteen or twenty feet, but there were sure footholds and one could disappear in a second. At the bottom of this hole was a little cave, very close and dark, in which one could sit or crouch. On the floor of this cave I picked up a knife, and, bringing it to the light, I recognised the carved blade, which I had seen Tortue once polish upon his thigh in the red light of a candle. The cave, upon inquiry, was discovered to be well known amongst the smugglers, though it was kept a secret by them, and they called it by the curious name of Issachum-Pucchar.