in it, as shown by
Dr. Heaton (Proc. Brit. Assoc., 1869, p. 127). Similar forms also occur
on a larger scale in some agates, and the artificial cells of Traube may
probably be regarded as analogous phenomena.

The aggregates of globular bodies seen in the section so greatly resemble
the globulites of slags and natural glasses, and in their arrangement so
forcibly recall the structures seen in the well known pitchstone of
Corriegills in Arran, that one is tempted to regard them as indicating
the beginnings of the development of crystalline structure in the
tabasheer. But I have good grounds for believing the structure to have a
totally different origin. They seem in fact to be the portions of the
mass which the fluid Canada balsam has not succeeded in penetrating. By
heating they may be made to grow outward, and as more balsam is imbibed
they gradually diminish, and finally disappear.

I must postpone till a future occasion a discussion of all the structures
of this remarkable substance and of the resemblances and differences
which they present to the mineral opals on the one hand, and to those of
the opals of animal origin found in sponge spicules, radiolarians, and
the rocks formed from them, some of which have recently been admirably
investigated by Dr. G.J. Hinde (Phil. Trans., 1885, pp. 425-83).

I cannot, however, but think that it would be of the greatest service to
botanists, physicists, and mineralogists alike, if some resident in India
would resume the investigations so admirably commenced by Dr. Patrick
Russell nearly a century ago; and it is in the hope of inducing some one
to undertake this task that I have put together these notes. There are
certain problems with regard to the mode of occurrence of this singular
substance which could only be solved by an investigator in the country
where it is found.

[Illustration: SECTION OF INDIAN TABASHEER, SEEN WITH A MAGNIFYING POWER OF
250 DIAMETERS.]

Most parcels of the commercial tabasheer appear to contain different
varieties, from the white, opaque, chalk like forms through the
translucent kinds to those that are perfectly transparent. It would be of
much interest if the exact relation and modes of origin of these
different varieties could be traced. It would also be important to
determine if Brewster was right in his conclusion that the particular
internodes of a bamboo which contain tabasheer always have their inner
lining tissue rent or injured. The rep