of London, undertook an analysis
of tabasheer, the specimens being supplied from Brewster's collection
(_Edinburgh Journal of Science_, vol. viii., 1828, p. 335). His
determinations of the specific gravities of different varieties were as
follows:

Chalky tabasheer. 2.189
Translucent tabasheer. 2.167
Transparent tabasheer. 2.160

All the varieties lose air and hygroscopic water at 100 deg. C., and a larger
quantity of water and organic matter (indicated by faint smoke and an
empyreumatic odor) at a red heat. The results obtained were as follows:

Loss at 100 deg. C. Loss at red heat.
Chalky tabasheer. 0.838 per cent. 1.277 per cent.
Translucent tabasheer. 1.620 " " 3.840 " "
Transparent tabasheer. 2.411 " " 4.518 " "

Dr. Turner found the ignited Indian tabasheer to consist almost entirely
of pure silica with a minute quantity of lime and vegetable matter. He
failed to find any trace of alkalies in it.

In 1855, Guibourt (_Journ. de Pharm_. [3], xxvii., 81, 161, 252; _Phil.
Mag_, [4], x., 229) analyzed a specimen of tabasheer having a specific
gravity of 2.148. It gave the following result:

Silica. = 96.94
Potash and lime. = 0.13
Water. = 2.93
Organic matter. = trace

Guibourt criticised some of the conclusions arrived at by Brewster, and
sought to explain the source of the silica by studying the composition of
different parts of the bamboo. While the ashes of the wood contained
0.0612 of the whole weight of the wood, the pith was found to contain
0.448 per cent., the inner wood much less, and the greatest proportion
occurred in the external wood. On these determinations Guibourt founded a
theory of the mode of formation of tabasheer based on the suggestion that
at certain periods of its growth the bamboo needed less silica than at
other times, and that when not needed, the silica was carried inward and
deposited in the interior.

In the year 1857, D.W. Host van Tonningen, of Buitenzorg, undertook an
investigation of the tabasheer of Java, which is known to the natives of
that island under the name of "singkara" (_Naturkundig Tijdschrift voor
Nederlandsch Indie_, vol. xiii., 1857, p. 391). The specimens examined
were obtained from the _Bambusa apus_, growing in the Residency of
Bantam. It is described as resembling in appearance the Indian
tabasheers. Its analysis gave the following result:

Silica.