PART 3.] 
Hochsieller, Geology of Nkolars. 
G3 
serpentine, often traversed with veins of hornstone, and the same is the case with the thickly 
wooded mountain slopes, as far as could he observed in the small rocky beds of streams. 
The shore exhibited a very great variety in the color of the serpentine, jasper and hornstone 
pebbles : besides these, however, there were noticed also numerous pebbles of a dark green 
diallago rock, which must no doubt be in situ, somewhere on the same coast at no great 
distance. 
From the angular fragments of serpentine and other masses in the course of decom¬ 
position, a ferruginous breccia is formed at the foot of the hills, while in the breakers the 
serpentine gravels are being cemented by coral and shelly sand forming solid sandstone and 
conglomerate banks which recall the Verde-antique, (Ophiealcite). The plateau of the coast- 
reefs extends 2 to 300 feet from the precipitous shore into the sea. Tlio whole of tbe island 
was covered with thick piimeval forest which thrives well, even on the serpentine ground. 
In passing along there were observed on the southern part of tbe island and on the 
eastern coast thin-bedded rocks with a high dip; these were in massive cliffs almost perpen¬ 
dicular in the south-eastern bay with a columnar structure; their true nature remained, 
however, unknown to me, for I was unfortunately obliged to use the telescope in place of the 
geological hammer. 
Camorta, Trinkut, Nancowry with Katckall form the middle group of tbe 
Nicobar islands. Trinkut is situated in front of the eastern entrance of a channel between 
Camorta and Nancowry; it is a low island surrounded by coral, reefs, and on its southern 
coast whitish-yellow argillaceous marls crop out. Gamor t a xmA Nan cow ry exhibit a greater 
variety of formation.—PI. 4, Fig. 3.— Sections of Camortai and Trinkut. 1, Qabbro and 
Serpentine; 2, Breccia and tufa; 3, Clay marl with sandy beds; 4, Coral-rocks.—The 
channel between the two islands, the Nancowry haven, lias numerous small bays and 
corresponds with a transverse cleft, while the Trinkut channel is a longitudinal cleft. The 
precipitous shores of the former offer, therefore, the most instructive geological section. 
Tbe narrow western entrance to the Nancowry channel is marked by two projecting 
rocks, which have been washed out by the force of the waves, making thus a natural gateway 
of rocks. Both cliffs rising almost perpendicularly to about 80 feet, are formed of a coarse 
breccia, composed of angular fragments of serpentine and gabbro* firmly cemented. I could 
not observe any stratification in this rock on the Camorta side ; it is here in cliffs with largo 
quadrangular blocks. On the Nancowry side, however, coarser bands alternate with finer 
tufa-liko ones, with a strike from south-south-east to north-north-west and dipping about 85 
degrees towards west. On the Camorta side, there crop out at two places below heaps of 
masses of rocks, which Rink very properly regarded as friction-breccias, cliffs of a more 
or less serpentine or gabbro-like massive rock. 
Among the pebbles on the strand, 1 also met with numerous fragments of a reddish- 
brown rock traversed by white calcite veins, the rock which Rink called Eurite. 
These phenomena at the western entrance to the Nancowry-havcn are thus perfectly 
identical with those which Rink lias observed at the entrance of the Clala hay, situated only 
a few miles to the north ; they are represented (1. c. p. 68) by Rink in a section. Further 
to the north the mostly hare hills on the west coast of Camorta, recalling by their external 
shape conical volcanic forms, attain a height of from 4 to 500 feet; they no doubt indicate 
the further extension of the serpentine and gahhro-rocks, which on Camorta and Nancowry 
are traversed from south-south-east to north-north-west by a longitudinal cleft. 
In the interior of the Nancowry haven, wherever the rocks are exposed on the project¬ 
ing angles, they appear to be well-bedded, whitish-yellow, clayey marls, alternating with 
hanks of a fine-grained sandstone, with serpentine and gabhro tufas. 
Most instructive in this respect is the precipitous south-eastern corner of Camorta at 
which the coast line bends into the Trinkut channel. The argillaceous marl formation is 
here well exposed in cliffs of from 30 to 80 feet high. On the southern side of the corner 
the transverse section of the strata can be observed, dipping at 25° to 30° towards west, while 
on the eastern side, parallel to the longitudinal break, the beds crop out horizontally one 
above the other. The argillaceous marl does not contain fossils, is of a yellowish white color, 
* Gabbro is a rock composed of diallage, smaragdite or hypersthouc with labradorite or saussurite, and often 
some other minerals in an irregular mixture 
