There came three sudden raps on the table, loud and startling. These raps, I may explain, in the usual code mean “Yes.” As if to confirm it the pencil began to write again, and spelled out “Swallow-tail butterfly.” “Is that your name?” I asked. There was one rap, which signifies “No,” followed by three, which means “Yes.” I had not the slightest idea of what it all signified (indeed it seemed to signify nothing at all), but the sitting had become extraordinarily interesting if only for its very unexpectedness. The control was trying to establish himself by three methods simultaneously--by the voice, by the automatic writing, and by rapping. But how a swallow-tail butterfly could assist in some situation which was now existing in my house was utterly beyond me.... Then an idea struck me: the swallow-tail butterfly no doubt had a scientific name, and that we could easily ascertain, for I knew that there was on my shelves a copy of Newman’s _Butterflies and Moths of Great Britain_, a sumptuous volume bound in morocco, which I had won as an entomological prize at school. A moment’s search gave me the book, and by the firelight I turned up the description of this butterfly in the index. Its scientific name was _Papilio Machaon_. “Is Machaon your name?” I asked. The voice came clear now. “Yes, I am Machaon,” it said. With that came the end of the séance, which had lasted not more than an hour. Whatever the power was that had made Mrs. Forrest speak in that male voice and struggle, through that roundabout method of “swallow, swallow-tail, Machaon,” to establish its identity, it now began to fail. Mrs. Forrest’s pencil made a few illegible scribbles, she whispered a few inaudible words, and presently with a stretch and a sigh she came out of trance. We told her that the name of the control was established, but apparently Machaon meant nothing to her. She was much exhausted, and very soon I took her across to the house to go to bed, and presently rejoined Charles. “Who was Machaon, anyhow?” he asked. “He sounds classical: more in your line than mine.” I remembered enough Greek mythology to supply elementary facts, while I hunted for a particular book about Athens. “Machaon was the son of Asclepios,” I said, “and Asclepios was the Greek god of healing. He had precincts, hydropathic establishments, where people went to be cured. The Romans called him Aesculapius.” “What can he do for you then?” asked Charles. “You’re fairly fit, aren’t you?” Not till he spoke did a light dawn on me. Though I had been thinking so much of Parkes that day, I had not consciously made the connection. “But Parkes isn’t,” said I. “Is that possible?” “By Jove!” said he. I found my book, and turned to the accounts of the precinct of Asclepios in Athens. “Yes, Asclepios had two sons,” I said--“Machaon and Podaleirios. In Homeric times he wasn’t a god, but only a physician, and his sons were physicians too. The myth of his godhead is rather a late one----”