XIX. On the optical and physical properties of tabasheer. By David Brewster, LL. D. F. R. S. Lond. and Edin. In a letter to the Right Hon. Sir Joseph Banks, Bart. G. C. B. P. R. S. &c. &c. &c

Abstract

My Dear Sir, The substance called Tabasheer, has been long used as a medicine in Turkey, Syria, Arabia, and Hindostan. It was first made generally known in Europe by Dr. Patrick Russell, who published in the Philosophical Transactions, for 1790, a very interesting account of its natural history, and of the process by which it seems to be formed. From his en­quiries it appears, that this substance is found in the cavities of the bamboo, the Arundo bambos of Linnæus; and that it exists originally in the state of a transparent fluid, which ac­quires by degrees the consistency of a mucilage resembling honey, and is afterwards converted by gradual induration into a white solid, called Tabasheer. From the analysis of Mr. Macie (now Mr. Smithson), it appeared to be “perfectly identical with common siliceous earth.” The celebrated traveller M. Humboldt, discovered the same substance in the bamboos which grow to the west of Pinchincha, in South America, and a portion of what he brought to Europe in 1804, was analyzed by Fourcroy and Vauquelin, who found it to consist of 70 parts of silex, and 30 of potash and lime.