PART 8.] 
Blanford: Geology of Bombay Presidency. 
07 
At Karachi itself the only rocks seen belong to newer beds than any of those now 
described, but to the north-west near Magar Pir an impure limestone is met with, containing 
numerous mollusea and opereulina, but nummulites are scarce if they occur at all. From 
Karachi to Kotru (Kotree) various forms of nummulitic limestone cover the country. Near 
Ivotru itself white compact limestone with Alveolma is found, whilst to the westward, a 
considerable area is covered by the variegated sands and clays. Amongst these, north-west 
of Kotru, occurs the lignite of Lynyan, an attempt at mining which was once made. The 
quantity of the mineral was, however, found to be small owing to the rapid thinning out of 
the bed, and the quality was inferior. 
At Kanikot, a gorge in the Eri hills, twenty miles west of the Indus at Magendan, and 
forty-five miles north-west of Kotin, about 1,000 feet of massive alveolina limestone rests 
on 1,300 feet of variegated sands and clays, at the base of which trap is seen. Whether this 
trap be intrusive or not has not been ascertained ; it appears stratified and is slightly amyg- 
daloidal. Of course, the occurrence of igneous rocks below the lowest of the rocks known to 
be associated with the nummulitic limestones recalls the similar association of variegated clays 
resting upon traps, these unmistakeably belonging to the Deccan series, in Kaehh ; but it has 
by no means been definitely ascertained whether the trap in Sind is a representative of 
the Deccan series. The Eri hills are an outer ridge of the Hala range and terminate to 
the north at Sewan. The li.il;i range stretching along the frontier is said to be entirely 
composed of limestone. Further to the north, and to the north-west of Sewan, conglo¬ 
merates and sandstones of Sivalik age with mammalian bones are found along the flanks of 
the main limestone ranges. The greater part of Upper Sind is an alluvial plain. 
Laterite of the Deccan .—Although the age of the laterite found locally on the crest 
of the Sahyadri and in the southern Maratha country is extremely obscure, there appears 
some probability from its mode of occurrence that it should be referred to the older and not 
to the newer tortiaries. Its occurrence in isolated caps on various hills appears to indicate 
that all now seen is merely the remnant of a formation once far more widely spread, and its 
striking resemblance to the beds already mentioned as occurring in the Nummulitics of Surat 
renders it possible that the two may be of the same age. 
Laterite is essentially a clay strongly but unequally impregnated with iron peroxide, 
to which it owes its deep red coloui', which, however, is far from uniform, the surface of a 
freshly broken fragment being veined and mottled with different tints, from white to deep 
red. Sometimes the appearance is almost that of a breccia from the angular white frag¬ 
ments enclosed. In some places, as at Bidar, the rock is intersected by small irregular tubes, 
lined with hydrated peroxide of iron, but those are not always present. The surface has 
a very characteristic appearance, being very irregular, owing to the washing away of so much 
of the clay as has not been impregnated with iron, and being covered with a glazed coating 
of hydrated iron peroxide or brown hmmatite. In the newer forms of laterite (for the rock 
is of various ages) grains of quartz and small pisolitic ferruginous concretions are usually 
found in considerable numbers, but in the rock which occurs at high elevations in the Deccan 
these are often deficient. 
Of the origin of this singular rock but little can bo said. In consequence partly of 
its peculiar pseudo-scoriaceous appearance, and partly of its occasional passage into decom¬ 
posed trap at its base, it has by many geologists been classed with the volcanic rocks. But 
it has never been found intercalated with traps, and it is met with interstratified in the 
sedimentary Eocene strata; moreover, its conformity to the trappean flows is only apparent, 
since the same laterite is found in some places resting on traps much lower in position than 
in others, e. g., at Mahableshwar and Panchgain, it rests upon flows very high in the series, 
while at Matheran and Khandala it is found on much lower beds. It is therefore fairly 
evident that the Dcccan laterite is a rock of aqueous origin and newer than the volcanic 
