ADDENDUM The following was originally published as Part I of Bulletin XVI of the Boston Society for Psychic Research in April, 1932. The figure numbers listed herein refer to the illustrations in _Mental Radio_, with the exception of Figures 147, 148, and 149 which appeared in the Bulletin only. The author of the report was Dr. Walter Franklin Prince, Research Officer of the society. He was a doctor of divinity of the Methodist Episcopal Church and had been pastor of several churches. Later he retired and took up the work of the society. He died two years after this report appeared. THE SINCLAIR EXPERIMENTS FOR TELEPATHY About eighteen months ago I first opened a new book by the novelist Upton Sinclair, entitled _Mental Radio_, then newly issued. In 239 pages it outlined the story of the discovery and development of what purported to be a supernormal faculty possessed by his wife, and rehearsed a large number of experiments in which she seemed to have achieved a large and convincing percentage of successes as a telepathic “percipient,” the “agent” generally being Mr. Sinclair, but sometimes her brother-in-law or another person. I confess to misgivings as I began to read, first for the very reason that the writer is a novelist (unmindful of Wells and certain other writers of fiction who, nevertheless, have shown themselves capable of serious and even scientific thinking),[1] and secondly because I had suspected, rightly or wrongly, that once or twice in the past he had failed to discover the devices of certain clever professionals. To be sure, his wife was not a professional, and all the conditions could be under his own hand, but sometimes through sheer confidence people are deceived by their own relatives.