by the directive force of a lodestone. It was also believed that this effect might be produced although a stone wall intervened, so that a person outside a house or prison might convey intelligence to another inside.
This idea was perhaps the basis of the sympathetic telegraph of the Middle Ages, which is first described in the MAGIAE NATURALIS of John Baptista Porta, published at Naples in 1558. It was supposed by Porta and others after him that two similar needles touched by the same lodestone were sympathetic, so that, although far apart, if both were freely balanced, a movement of one was imitated by the other. By encircling each balanced needle with an alphabet, the sympathetic telegraph was obtained. Although based on error, and opposed by Cabeus and others, this fascinating notion continued to crop up even to the days of Addison. It was a prophetic shadow of the coming invention. In the SCEPSIS SCIENTIFICA, published in 1665, Joseph Glanvil wrote, 'to confer at the distance of the Indies by sym