Frontispiece and title-page of Francesco Redi’s “Experimenta naturalia,” Amsterdam, 1675, and two specimen pages of this treatise, referring to the snake-stones believed to be taken from the Indian _Cobras de Capello_, or hooded snakes. ] [Illustration: FORMS OF TABASHEER Bought at Fair at Calcutta, 1888, by Dr. Valentine Ball. ] Redi states that he himself possessed some of these stones, as did also Vincent Sandrinus, one of the most learned herbalists of Pisa. Redi describes them as “always lenticular in form, varying somewhat in size, but in general about as large as a farthing, more or less. In color some are black, others white, others black, with an ashy hue on one side or both,” etc. Up to the present time no one has apparently identified what Tavernier referred to in speaking of snake-stones. It, however, occurred to the writer, after receiving a quantity of tabasheer from Dr. F. H. Mallet of the Geological Survey of India, who obtained it at the bazaar of the Calcutta Fair in November of 1888, that many, if not most of the Hindu snake-stones must have been tabasheer. Tabasheer is a variety of opal that is found in the joints of certain species of bamboo in Hindostan, Burma, and South America; it is originally a juice, which by evaporation changes into a mucilaginous state, then becomes a solid substance. It ranges from translucent to opaque in color, and is either white or bluish-white by reflected light, and pale yellow or slight sherry red by transmitted light. Upon fracture it breaks into irregular pieces like starch. As in Tavernier’s account of its clinging to the palate and causing water to boil when immersed, it actually has the property of strongly adhering to the tongue, and when put into water emits rapid streams of minute bubbles of air. It has a strong siliceous odor, but after absorbing an equal bulk of water becomes transparent like a Colorado hydrophane described by the writer several years ago before the New York Academy of Sciences. Although tabasheer is mentioned in nearly all the textbooks, very little of it has reached the United States. It is highly interesting, since we have here an organic product scarcely to be distinguished from a similar opal-like body found by Mr. Arnold Hague in the geysers of the Yellowstone Park. Both tabasheer and the hydrophane were probably what was called “Oculus Beli,” “Oculus Mundi,” and “Lapis mutabilis” by Thomas Nicol, Robert Boyle, and other writers of the seventeenth century, and “Weltauge” by the Germans. The great capacity of this substance for absorbing a fluid would undoubtedly render it as efficacious for the purpose of absorbing poison as any other known stone, providing the wound were open enough; and its internal use to-day as a medicine is possibly also due to this property.