s stated that a bamboo grown in a hot-house at
Islington gave a rattling noise, and on being split open by Sir Joseph
Banks yielded, not an ordinary tabasheer, but a small pebble about the
size of half a pea, externally of a dark brown or black color, and
within of a reddish brown tint. This stone is said to have been so hard
as to cut glass, and to have been in parts of a crystalline structure.
Its behavior with reagents was found to be different in many respects
from that of the ordinary tabasheer; and it was proved to contain silica
and iron. The specimen is referred to in a letter to Berthollet published
in the _Annales de Chimie_ for the same year (October, 1791). There may
be some doubt as to whether this specimen was really of the nature of
tabasheer. If such were the case, it would seem to have been a tabasheer
in which a crystalline structure had begun to be set up.

In the year 1806, MM. Foureroy and Vauquelin gave an account of a
specimen of tabasheer brought from South America in 1804 by Humboldt and
Bonpland (_Mem. de l'Inst_., vol. vi., p. 382). It was procured from a
species of bamboo growing on the west of Pichincha, and is described as
being of a milk white color, in part apparently crystalline in structure,
and in part semi-transparent and gelatinous. It was seen to contain
traces of the vegetable structure of the plant from which it had been
extracted. On ignition it became black, and emitted pungent fumes.

An analysis of this tabasheer from the Andes showed that it contained 70
per cent. of silica and 30 per cent. of potash, lime, and water, with
some organic matter. It would, perhaps, be rash to conclude from this
single observation that the American bamboo produced tabasheer of
different composition from that of the Old World; but the subject is
evidently one worthy of careful investigation.

It was in the year 1819 that Sir David Brewster published the first
account of his long and important series of observations upon the
physical peculiarities of tabasheer (Phil. Trans., vol. cix., 1819, p.
283). The specimens which he first examined were obtained from India by
Dr. Kennedy, by whom they were given to Brewster.

Brewster found the specimens which he examined to be perfectly
_isotropic_, exercising no influence in depolarizing light. When heated,
however, it proved to be remarkably _phosphorescent_. The translucent
varieties were found to transmit a yellowish and to reflect a bluish
white ligh