LATERITE AND ITS VARIETIES. 
259 
above locality. “The ferruginous sandstone 
is the lowermost, and has a great degree of 
compactness, so as to fit it for architectural 
purposes, in which it seems to be largely 
employed. It is evidently stratified, the strata 
being nearly horizontal ; the quartz particles 
are agglutinated by a ferruginous cement. 
“ The sandstone, nearly in the whole extent 
of the hillock, supports a lithomarge of a 
whitish or flesh colour, sometimes having a 
bluish tint. The stratum of this earth is not 
very thick, and in many places, it is overlaid 
by a purple red, compact, slaty, haematiticiron 
ore, which passes insensibly in the upper part 
into a cellular rock, full of tubular sinuosities, 
very much similar to the laterite. In some 
places this ore lies immediately over the sand- 
stone, without the intermediate litho- 
marge.”* 
These three minerals, then, are plainly 
discoverable in these imbedded masses of 
conglomerate sandstone, but there is an 
argillo-ferruginous cement uniting the whole 
together. This cement gives the colour to 
the entire mass, which is of a purple-red hue, 
as mentioned above, and sometimes has a 
bluish tinge (No. 3). Frequently it presents 
varieties, being either finer or coarser grained 
(Nos. 4and5). The quartz is. very abund- 
ant ; the lithomargic earth scanty, and the 
mica is met with in small disseminated 
scales, “ few and far between.’’ The ori- 
ginal sandstone rock, then, of which these 
nodules are fragments, must have resulted 
from the fracture and disintegration of some 
still more ancient crystallized rocks. The 
sandstone, thus formed, being, in its turn, 
disrupted, the fragments were tossed and 
rolled about by some aqueous catastrophe, 
until they became imbedded in this laterite 
(so called), or conglomerate rock which we 
now see. This view of the case, indicates 
violent disturbing forces, occurring at two 
distinct periods of time. Besides the sand- 
stone, fragments of ochrey iron ore, to be 
hereafter mentioned, were found imbedded in 
the clay. 
I was unable to trace the appearance of 
stratification elsewhere than in this nullah. 
The ground rises abruptly from its banks to 
the N. W., forming one of the eminences 
bounding the lake on that side, and the rock 
changes character from what I have describ- 
ed above, as occurring in the bed of the 
nullah. Instead of seeing merely the sand- 
stone nodules imbedded in clay, we have a 
rock possessing the more characteristic qua- 
lities of laterite (No. 6). It is rendered ca- 
vernous by tortuous cavities, which penetrate 
it in all dii*ections, sometimes filled with red 
or yellow ochraceous earth ; sometimes with 
a white clay, like decomposed felspar ; but fre- 
quently they are quite empty, which is caused, 
it appears to me, by water percolating from 
above, carrying with it the soft substance 
of these earths, the spaces they once filled 
being thus rendered void (No. 7). 
* Jovrnal ‘S the Asiatic So icfy qf Bengal, 
August .S3b, p . 437. 
This laterite still shows evident traces of 
the sandstone, described as found, in such 
large fragments, imbedded in the walls of 
the nullah ; but the pieces are much rounded 
and comminuted, and are united together by 
a very compact, heterogeneous, kind of paste, 
composed apparently of the debris of the 
sandstone itself, of iron ores, and of the 
lithomargic earth. d'here is no mistaking 
the sandstone, which may be picked out, 
in pieces of the size of a walnut, from the 
centre of a mass of the laterite, and clearly 
shews the same structure as that of the 
nullah (No. 28). 
Pebbles, of various kinds of crystallized 
rocks, are met imbedded in the hardest and 
most compact laterite. On the rising grounds 
to the north of the lake, I picked out frag- 
ments of white quartz rock, some pieces an- 
gular, others much rounded (No. 9) ; of very 
compact siliceous sandstone, of a red .colour, 
so hard as to be broken difficultly with a heavy 
hammer (No. lO), and of a white, granular, 
friable, disintegrating sandstone (No. 11.). 
Added to these, a great profusion of fragments 
of ochrey iron ore, red and brown (Nos. 12 and 
13), a good deal of it slaty (No. 14), are found 
imbedded in the less compact kind of laterite, 
and in the gravel. This ore, I think, contri- 
butes to form the more compact laterite, also, 
but it appears to have been more broken and 
subdivided, and is therefore not so easily trace- 
able. 
The latei'ite varies very much in appearance. 
Sometimes it is very hard, compact, and heavy, 
highly ferruginous, of a deep red colour, pene- 
ti-ated in all directions by the sinuosities con- 
taining the red and yellow and white earths. 
In this kind the red sandstone nodules are 
very distinguishable (No. 15). Some masses 
are nearly half composed of the white litho- 
margic earth, which renders it very crumbling 
(No. 16). 
Other varieties exhibit a pisiform structure, 
numerous rounded pebbles being united toge- 
ther by a yellow clayey cement ; this seems of 
recent origin (No. 17). 
Again, in many superficial situations, it is a 
mere gravel, possessing very little coherence, 
and, apparently, formed from the debris of 
the laterite itself. The pebbles, composing 
this gravel, still exhibit the structure of the 
red conglomerate ' sandstone, and of the 
ochrey iron ore (Nos. 18 and 19). 
Innumerable pebbles strew the face of the 
ground, in all directions, a great number of 
which, on fracture, display the structure of the 
nodular imbedded sandstone (No. 20). I 
should observe, that I no where saw this sand- 
stone in any other form than that of frag- 
ments imbedded in the laterite, or detached 
thence, and undergoing another rolling pro- 
cess on the present sui-face of the ground. 
Equally numerous are the scattered frag- 
ments of ochrey iron ore, described above. I 
no where found this substance as a vein, or 
in mass. It would seem probable that it 
existed in the original crystallized rocks ; and 
that, under the watery disrupting influences, 
to which the whole ingredients of the formation 
