called Tabaxir or Tabasheer, which is supposed in the East Indies (probably because it is rare and difficult of acquisition, like the imaginary stone in the head of a toad) to be endowed with extraordinary virtues. Some of it, brought to England, underwent a chemical examination, and proved, as nearly as possible, pure flint. See Dr. Russell's and Mr. Macie's papers on the subject in the Phil. Trans. for 1790 and 1791. It is even found occasionally in the Bamboo cultivated in our hot-houses. But we need not search exotic plants for flinty earth. I have already, in speaking of the Cuticle, chapter 3d, alluded to the discoveries of Mr. Davy, Professor of Chemistry at the Royal Institution, on this subject. That able chemist has detected pure flint in the cuticle of various plants of the family of Grasses, in the Cane (a kind of Palm) and in the Rough Horsetail, Equisetum hyemale, Engl. Bot. t. 915. In the latter it is very copious, and so disposed as to make a natural file, which renders this plant useful in various manufactures, for even brass cannot resist its action. Common wheat straw, when burnt, is found to contain a portion of
