Home › Magic Stones and Electric Gems › Magic Stones and Electric Gems: Lemery

Magic Stones and Electric Gems: Lemery

The attractive properties of the tourmaline are said to have been first brought to scientific notice by M. Louis Lemery, in a report made during 1717 to the French Academy of Sciences; however, Lemery was inclined to attribute them to magnetic influence. That these phenomena of attraction and repulsion were really due to the electric properties of the stone was first clearly brought out by the German physicist, Franz Ulrich Theodor Aepinus, and his conclusions were communicated to the Berlin Academy of Sciences in 1756. Aepinus made his experiments upon two specimens of tourmaline from Ceylon, which had been furnished him by Lehmann, a fellow-member of the Berlin Academy, who, as Aepinus frankly admits, first drew his attention to the electric action of the stone. That not only friction but heat also should develop the electric energy, both positive and negative, of the tourmaline, serves to differentiate it from many other potentially electric substances, in the case of which friction alone is effective.

The specimen shown by M. Lemery to the French Academy of Sciences in 1717 is stated to have come from "a river in the Island of Ceylon," and is described as being of small size, flat, orbicular, quite thin, of a brown color, and smooth brilliant surface. Its peculiar property of attracting and then repelling ashes or iron filings as well as bits of paper, was duly noted. This specimen had cost M. Lemery 15 livres. After reciting the constant repulsion and attraction exercised by a magnet upon the needle, the attraction by the opposite pole, and repulsion by the same pole, he proceeds to remark that this Cinghalese stone acted quite differently, since it first attracted and then repulsed the same object presented in the same way. This intermittent or irregular action was in his opinion to be explained by the theory that a vortex was intermittently developed in the substance. As it begins the small bodies are attracted, when it ceases they remain stationary, but when it is renewed "and there emanates from the stone a material analogous to the magnetic emanation" then the bodies are repulsed. Another peculiarity was that the body which had been repulsed could not again be attracted, whence the conclusion was arrived at that the stone's repellent force was superior to its attractive power. These necessarily somewhat inexact observations are interesting as marking one of the earliest attempts to explain these phenomena, even although the explanation is faulty.

The great French crystallographer, Abbe Hauy, relates his experiments on a tourmaline crystal. He set this crystal in steel clamps, with a long stem which was inserted in a wooden handle, and then subjected the tourmaline to the heat of a brasier. As the heat augmented and penetrated the stone, its natural electric force became decomposed, the two component fluids being forced to separate from each other. It was now necessary to cool the tourmaline off a little; when too much heated the electrical phenomena were interrupted; they were also diminished in intensity when the stone became cool again. The perfect crystal chosen for experiment clearly showed the negative and positive electrical poles; even the smallest pieces showed this, and, indeed, if a very small piece were broken off the positively electric side of a crystal, it would preserve this positive electricity and soon develop a negative electricity also.

We may be somewhat loath to doubt the tale that little Dutch children were the first to note what to them was the queer action of some bits of tourmaline, but preference should probably be given to the statement that the discovery of the electric phenomena induced by heating in these stones was due to the fact that some Dutch jewellers put specimens of tourmaline in the fire to test their hardness, and then found that the stones attracted or repelled the ashes of the fire.