Excerpt from "Worlds Without End" by Philip Ball, published on December 10, 2015. William Barrett was puzzled by flames. As the young assistant of the eminent John Tyndall at the Royal Institution in London in the 1860s, he noticed that flames seemed to be sensitive to high-pitched sounds. They would become flattened and crescent-shaped, as Barrett put it, like a "sensitive, nervous person uneasily starting and twitching at every little noise". He was convinced that this "unseen connection" was mediated by some immaterial intangible influence it was, he admitted, an effect "more appropriate for a conjuror's stage than a scientific lecture table". - Certain people, Barrett decided, were analogues of the sensitive flame, exquisitely attuned to vibrations that others could not perceive, to "forces unrecognized by our senses". He considered these persons able to receive messages from supernormal spirit-beings existing in an intermediate state between the physical and the spiritual - a phenomenon that might account for telepathy. Source: "Worlds Without End" (https://publicdomainreview.org/essay/worlds-without-end)​