622 
THE CONTOUR OF THE ROCKS OF THE NEELGHERRIES. 
logical interest than any other group in this 
extensive region. 
Their being almost in the middle of a 
district, in which one of the most interesting 
rocks in the Indian formations (the laterite) 
is found developed in all its characteristic 
features, adds not a little to their importance 
in a geological point of view. On account 
of their superior elevation, they ought to 
be carefully e.xamiued by the geologist, 
before he extends his researches to the other 
parts of the chain, of which they form the 
most elevated point. Dr. Benza says 
that the experienced eye of the geolo- 
gist can easily guess the nature of the 
rock composing a hill ora system of hills, by 
the simple inspection of its outlines : thus, 
spiry peaks show the formation to be pri- 
mitive ; rounded smooth outlines are indica- 
tive of calcarious mountains ; while the 
castellated ruin4ike appearance of a moun- 
tain is proper to the sandstone formation. 
Although the contour of the rocks 
forming the Neelgherries is even, smooth, 
rounded, and, as it were, undulating, the 
fundamental rocks of which they are 
composed belong to the primitive class. 
Their outline resembles those hills and 
eminences we meet in districts, resulting 
from tertiary or alluvial deposits. What t})e 
rock is, which gives those hills the rounded 
form they exhibit, will be shewm hereafter. 
With the exception of some vertical cliffs 
and mural precipices, seen in the boundaries 
of this elevated plateau, and a few project- 
ing masses of the fundamental rocks on the 
summits and declivities of these hills, the 
whole group is uniformly covered by a thick 
stratum of vegetable earth (No. 1*), which, 
overlaying a thicker stratum of red earth 
(to be described in the sequel), supports 
numerous plants, chiefly grasses, which, 
growing most luxuriantly in thick contigu- 
ous tufts, give the surface a smooth carpet- 
like appearance. This vegetable earth in 
general is clay, and of a grey colour, and 
* The figures refer to illustrative specimens 
presented tor deposit in the Mineralogical 
Cabinet of the Madras Literary Society - 
Editor. 
very friable. On this soil we occasionally 
see small rounded pieces of the decomposed 
subjacent rock, bestrewed particularly on 
those spots where blocks of the decomposing 
rocks are seen jutting through the soil. 
This vegetable soil is replaced in the low 
valleys and flats at the foot of the hills, by 
a black soil, such as we frequently see form- 
ing the peat-bog in swampy grounds, in 
which a large quantity of vegetable matter is 
being decomposed. This soil is of a black, or 
deep browui colour; of tenacious consistence, 
when moist ; crumbling into powder, and 
often splitting into prismatic masses, when 
dry. At first sight it resembles the black 
soil of the plains of India. From this 
last, however, it seems to differ greatly, 
in containing a large quantity of carbona- 
ceous matter, and much oxide of iron. To 
deprive this black soil of the greater 
portion of its humidity. Dr. Benza exposed 
it to a heat, sufficient to melt lead, and, 
after having weighed a certain quantity 
of it, subjected it to an intense heat 
for an hour ; after this, it had lost more 
than 25 per cent, of the original w^eight, and 
had changed into an ochrey red powder. 
In many other localities the author 
remarked a most luxuriant vegetation of 
innumerable ferns, of which the roots 
are seen decaying into a black powder. 
Our author’s attention was greatly excit- 
ed to see (at Kotagherry) those tubular 
bodies traversing the thick stratum of black 
earth, which overlays the yellow clay, with- 
out having a particle of it in their composi- 
tion. As if the roots, by a kind of capillary 
attraction, sucked up through the black 
soil, without mixing with it, the particles 
of the yellow clay which, undisturbed by the 
vicinity of the black soil, arranged them- 
selves concentrically to the root ; and the 
latter decaying has left the cavity of the 
tube empty. 
Immediately below the vegetable soil, in 
almost all places, we find a stratum of de- 
tritus (in general not above a few inches 
thick), which is different in different loca- 
lities, according to the nature of the rock 
