i 283 1 
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. 
Read May 6, 1819. 
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 en- 
quiries it appears, that this substance is found in the cavities 
of the bamboo, the Arundo hambos of Linnaeus ; and that it 
exists originally in the state of a transparent fluid, which ac- 
quires 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 <f 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.-f 
* See Philosophical Transactions for 1791, p. 368. 
f Mdmoircs de VInstitut, Tom. vi. p. 382. 
