64 
Records of the Geological Survey of India. 
[vol. it; 
and on tlie perpendicular walls it was covered with inch-long, white, very thin, crystals of a 
silky lustre. The examination of these showed them to be sulphate of magnesia. The 
clay itself contains, according to Rink’s analysis, besides silicate of alumina, iron-oxide 
and magnesia. 
The whitish-yellow clay marls of Camorta and Nancowry being entirely free of lime 
have become famous since Professor Elirenberg (Berl. Akad. Monatsberichte 1850, p. 476), by 
an examination of the samples brought by Dr. Rink, has shown that they are true Polycistina- 
marls, like those of the Barbados. Elirenberg discovered in 1848 about 300 species, which 
were by Professor Forbes believed to belong to tniocene (tertiary) deposits. Elirenberg says: 
“ Especially well developed is this material on Camorta, where, near Frederickshaven, a 
bill 300 feet bigh is covered all over with variegated Polycistina-ciny, while the Mongkata 
hills on the eastern side of the island are according to Rink entirely composed of a whitish- 
clay resembling meerschaum ; this is, according to my analysis, a nearly pure agglomerate 
of beautiful Polycistina and .their fragments, beside numerous Spongiolites."* The species of 
Polycistina on the Nieohars are, according to Elirenberg, the same which compose the 
similar marl on the Barbados, situated in noarly the same latitude ; but there are also some 
new forms. 
Near the level of the sea, the clay marls, which locally contain angular fragments of 
serpentine and gabbro, alternate with more solid strata of a psephitic rock, which is com¬ 
posed of strongly-cemented angular fragments of serpentine and gabbro, and can therefore 
be best designated as gabbro-tufa. It is remarkable that this rock again includes larger 
and smaller pieces of the clay marl. On the eastern coast, near the village Inaka (Enaca) 
a reddish micaceous sandstone appears between the clay marls. 
Similar are the geological conditions on the northern coast of Nancowry. Between the 
villages Imiang and Malacca, the whitish-yellow clay marls crop) out in slightly inclined 
strata ; between Malacca and Injaong, however, lies a precipitous cliff, on which these strata 
rise almost perpendicular, and _are gradually replaced by an accumulation of fragments of 
serpentine and gabbro. At the projecting corner itself, the traveller faces a precipitous 
cliff of about 60 feet in height, but being cracked and decomposed, the true nature of 
the rock is recognised with difficulty. On a fresh fracture, however, one soon observes a 
massive diallage rock, the laminar diallage being clearly traceable in the nearly solid mass 
of felspar. Narrow veins of quartz pass through the rock. 
From here up to the village Injaong the strand is again Hatter, and nowhere nearer 
than on the other side of the village high, dark-colored, rocks are a second time visible, 
indicating a massive rock. These are the two places which Rink also has marked on his 
maps as plutonic rocks. 
Trice and Trade. —On the north-western point of the small island Trice, highly up- 
heaved banks of a fine-grained argillaceous sandstone of a greenish-grey color form a 
low precipitous shore. The same stratified rocks alternate with fliin-bedded sandy slates, 
showing on the south-eastern coast margin of the small island Track, only a few cables 
length distant, the accompanying section. Pi. 4, Fig. 4. Besides a fault, the strata form 
a saddle and strike from south-south-east to north-north-west. In a sandstone bank I found 
here imbedded a. rolled fragment of a bituminous coal, the same of which 1 met with a larger 
but equally rolled fragment on the strand of the island Trice. Of coal seams there was, how¬ 
ever, no trace to be detected; what might be mistaken for them from a distance was only the 
shadow of softer sandstone banks deeply weathered out, or the darker color of some strata. 
Palo Milu. —A small island on the northern coast of Little Nicobar, which Dr. 
Rink has so excellently described in all its peculiarities, consists, in the higher parts, of a grey, 
fine-grained, micaceous and calcareous sandstone in massive banks. Very often spheroidal 
concretions are to be observed showing on the soft weathered surface like cannon balls. No 
trace of fossils could be found. The massive banks have thin-bedded sandy slates interstra- 
tified. The strata strike from south-south-east to north-north-west, dipping to east at 
an angle of 45 degrees. Dr. Rink (loc. cit, p. 50) mentions a fossil resin in the sandstone 
of Milu. 
* The result of examination of a Nancowry specimen is figured on Plate XXXVI of EUreuberg’s 1 Hikro- 
geologie,* 
