626 
KOONOOR— DYKE OF BASA-LT. 
the right of the path, our author perceived a 
small knoll, forty or fifty feet above the level 
of the river, extending from the S. W. On 
the uppermost convexity of this knoll, are 
erected two enclosures for cattle, now 
probably deserted, no human habitation, 
for miles round the place, being seen. 
The floor of these enclosures is formed 
by an immense ledge of rock, which, in their 
interior, is level with the soil, and on the 
outside, rises a few inches above it. The 
rock appears unstratified, at least what is 
visible of it, and its composition is the fol- 
lowing : lamellar garnets, some of them half 
an inch in diameter, which have the 
appearance of the dodecahedral species of 
that mineral — cinnamon-stone, or essonite. 
Of all these minerals it seems that the 
cinnamon-stone is the most liable to decom- 
pose, or disintegrate ; since we see, in some 
parts of the surface of the mass, small cavi- 
ties, in consequence of the falling out of 
the disintegrated crystals of this mineral. 
This rock is very compact, exceedingly 
heavy, and takes a brilliant polish. 
In the Koonoor pass, not more than a 
mile from the bridge down the pass, and just 
below the village of Koonoor, in the road, 
many of the blocks which have been blasted, 
are traversed by a dyke of basalt. This 
basalt is very compact ; has a dull, even 
fracture ; but, in one portion of the dyke, 
Dr. Benza, had the opportunity of observing 
that the part which was in contact with the 
granite had the appearance of a crystalline 
hornblende, which passed into compact 
hard basalt towards the centre of the dyke. 
Another enormous dyke of this rock is 
seen in the chain of hills which connects 
Doodabetta with Kaitee pass. The summit 
of the hill, which is between’ those two 
mountains, is formed of basalt in huge 
masses, some of which affect the prismatic 
figure. In general the large blocks are not 
so compact as the thin ramifications of the 
dyke traversing the rock, but the horn- 
blende in the former is nearly granular and 
shining, somewhat approaching primary 
greenstone. About two miles from Ootaca- 
mund, along the Neddiwattum road, there 
is a small rivulet, close to the road, the 
first met in this direction. A basaltic 
dyke, like a ledge, half in the water 
and half out, is seen in an oblique po- 
sition, N. E. and S. W. dipping north. 
On ascending to the summit of this hill, 
which extends in the usual rounded form 
eastward, we see that it is entirely formed 
of basalt, in a dyke probably a diramation 
of that of the rivulet, and extends all along 
the small ridge for nearly a quarter of a mile. 
Basaltic dykes are not rare in those pla- 
ces, which Dr. Benza had an opportunity 
of visiting in the plains of India. He has 
seen them through granite and gneiss in 
Mysore ; through porphyry, near the euritic 
hill of Pallicondah ; through hornblende 
slate, near Mateepolliam ; through por- 
phyry, near Garabunda (Northern Circars), 
and in many other places. Following 
the Koondah road, in less than a mile 
we come upon the continuation of the 
magnetic iron ore, which, intersecting the 
lake, extends to this place, very much alter- 
ed in appearance and composition, looking 
more like a stratified ferruginous sandstone, 
than the continuation of the metallic vein 
near the lake, many of the strata being con- 
torted and waving and containing hardly 
any metal. Descending from the eastera 
Koondah pass, and crossing the field, a little 
knoll is seen, traversed by a basaltic dyke in 
an east and west direction ; it is flanked 
by, and has burst through, sienitic granite, 
crossing the road : on ascending the 
ridge opposite to the Avalanche, this land- 
slip comes at once to view. There has 
evidently been no sinking of the land in the 
declivity of the hill; but it seems that a thick 
stratum of the rock, lying almost vertically 
on the declivity of the hill and between 
which and another the present rivulet runs, 
whose waters having undermined the stra- 
tum (which might have overlaid thick beds 
of clay, the result of the decomposed rock), 
the w’eight of the superincumbent mass, 
together with the almost vertical position of 
the stratum, made it slip — hurling rock, 
soil, and jungle into the valley below, leav- 
ing a deep ravine, bounded to the north by 
a mural precipice of undecomposed rock„ 
