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A finely granular limestone composed of minute crystals of
calcite with patches of coarse mosaic of calcite scattered
through it, which are often circular or oval in form and
sharply defined from the matrix. They appear to be replace-
ments of some calcareous organism. In addition, fragments
of molluscan shells are seen in section.

The residue left after solution in acid consists of crypto-
crystalline growths of silica resembling flint and sometimes
taking the form of sponge spicules.

Foreign minerals introduced from without are rare ;
occasional minute flakes of muscovite, a little hornblende, and
rutile have been observed. Small grains of ferric hydrate
are, however, numerous.

This and specimen (01) are from the same stratified rock
at the pass, Bêl-tâgh.

5. Taklamakân Desert, S. of Marâl-bâshi. C. xxiv.
Quartz Grit.
A fine-grained almost red quartz grit composed almost entirely of
grains of quartz, most of them angular ; comparatively few

rounded. They are all well defined by a thin continuous
coating of ferric oxide. The quartz sometimes contains
minute crystals of an undetermined mineral and vapour
cavities. A few grains are composite, minutely mosaic, and
recall the basis of some granophyres.

Grains of felspar are fairly numerous ; some are microcline,
quite fresh and unaltered, some oligoclase, and many are too
much sericitized for determination.

In addition to ferric oxide there are patches of a black
opaque mineral.

This rock is also met with as broken flakes included in
the fragments of rock-salt described under No. 2 a.

6. Mazâr-tâgh of Khotan (052). Red Grit.
An extremely fine-grained grit consisting chiefly of minute
angular particles of quartz cemented by ferric hydrate and
calcium carbonate.

Associated with this are several specimens (053-058) of
gypsum.

LOP DESERT

7. Camp C. civ (01). Amphibolite.
A compact dark green rock composed almost entirely of
hornblende with an angle of extinction of 22° and pleochroism :
X, faint yellow to almost colourless ; Y, dark sage green ;
Z, dark green. Biotite is absent, but a little muscovite occurs
as an interstitial constituent.

Anorthite and labradorite are scattered through the rock in
small allotriomorphic grains. Zoisite is present often in well-
formed crystals, and there is a small quantity of magnetite
with sometimes associated sphene.

7a. An incrustation covering the ground, two to four
miles SE. of C. civ (01). A thin porous layer of gypsum
coated on one surface with an irregular compact layer of the
same mineral.

8. Camp C. civ (04) from 'Sai' about thirteen miles SE.
of C. civ. Vosgésite.
The specimen is an irregular rod of a grey rock speckled
with minute black grains (hornblende) and comparatively
large phenocrysts of white felspar, quartz, and biotite or horn-
blende. It has been polished by the wind and worn into little
pits corresponding with the presence of felspar phenocrysts.

The ground mass consists chiefly of plank-like sections of
albite and orthoclase with numerous elongated prisms of
hornblende and interstitial quartz. Magneite is present
throughout. The albite is much altered by weathering, with
the development of minute grains which give it a milky white
appearance by reflected light. The hornblende presents the
forms (110), (100), and (010) ; it extinguishes at 19°, and its
pleochroism is, X, faint brownish yellow, almost colourless ;
Y and Z, yellowish brown. It is irregularly dispersed, while
the felspar frequently presents a radiate or sheaf-like arrange-
ment and sometimes occurs as elongated forms included in
quartz which recall some of the radioles met with in grano-

phyre. The phenocrysts are hornblende, biotite, oligoclase,
and quartz, the latter two of great size in comparison with
the constituents of the matrix.

The biotite is brown when fresh and strongly pleochroic :
X, light yellow ; Y and Z, warm brown. It includes large
crystals of apatite and some magnetite, is often much corroded
by the matrix, and in many cases has suffered by alteration,
and is then green in colour, with pleochroism : X, very faint
green ; Y and Z, deep green. The change is accompanied
by the development of epidote.

The oligoclase occurs in single crystals or crystal com-
plexes, is often zonal, much corroded by the matrix, and
sometimes invaded by it.

The quartz occurs in single individuals or as a coarse
mosaic : in one instance a reaction rim is present, formed by
an intergrowth of quartz and chlorite. The chlorite appears
to have resulted from the transformation of the adjacent
hornblende.

9. From the same locality as No. 8. Mica schist.
A long thin parallel-sided rod of fine-grained mica schist,
composed of quartz, abundant biotite with pleochroism : X,
colourless ; Y and Z, brown, some muscovite and iron oxide.

9. a. (05, 06). Two worn crystals of pure quartz.

10. From stony 'Sai', sixteen miles SSE. of C. civ. (07
and 08) mica schist ; (09 and 010) quartz.

11. C. civ (011). Granophyre.
Ground mass micrographic and pilotaxiitic, with phenocrysts
of orthoclase, oligoclase-albite, quartz, and biotite. The
felspars and quartz lie severally in the middle of an area of
micrographic structure, the growth of which they seem to
have initiated. The quartz has been corroded by the
matrix, and the felspars are crowded with minute granules.

The biotite is present in fragmentary remains represented