part 1.] Stanford: Great Indian Desert between Sind and Ttdjpntana. 17 
IV. —Summary op Geological Observations. 
Formations observed .—From the preceding account of the journey, it will be seen that 
in the tract traversed the following formations were distinctly identified:— 
9. Blown sand 
8. Alluvial deposits 
7. Nummulitie limestone 
6. Ammonitiferous beds of Kunhri 
6. Jesalmir limestones and sandstones 
4. Balmir sandstones ... 
3. Jodhpur sandstones... 
2. Shales and boulder bed of Lowo and Pol:ran 
1. Malani felsite, porphyries, syenite, &c. 
■ Post tertiary. 
Tertiary . 
^ Jurassic. 
? Vindhyan. 
? 
P 
Maldni beds .—It is evident that these, the oldpst rocks met with in the portion of 
the desert traversed, are volcanic. Their extremely silicious nature may be due to alteration 
but their porphyritio character, and the occasional occurrence of ash beds, sufficiently attest 
their volcanic origin. They consist principally of very silicious felsites, so hard that they 
are not scratched by quartz, and have frequently the appearance and texture of jasper. 
They vary greatly in colour, from black or dark-drown to pink, blue or white, the dark- 
coloured rock being always hard and undecomposed, whilst the lighter-coloured varieties 
are softer and appear to bo altered. The most constant character is the presence of small 
crystals of felspar, usually of a pink or red colour, in addition to which small grains of 
transparent silica are frequently dissiminated throughout the rock. 
In places diorito was found associated with these rocks, and in some of the hills west 
of Balmlr, coarsely crystalline granitoid syenite and pegmatite are intercalated in large 
masses with the porphyritio l'elsites. True granite may occur, but in the few hills examined 
mica was absent, although the character of the rock was distinctly granitic. The presence 
of similar granitoid rocks elsewhere is rendered probable by the occurrence of pebbles and 
boulders in some of the later beds. 
The Malani rocks must be very ancient, but no idea can bo formed of their geological 
position, as they are nowhere associated with rocks of known age except where underlying 
beds of comparatively recent date, and nothing resembling them appears hitherto to have been 
detected elsewhere in India. They form the hills extending upwards of 30 miles west of 
Balmir, and south as far as Chotan, 25 miles south-west of Balmlr, and north probably to 
Vinjorai, 35 miles south-south-east of Jesalmir. South of the BalnuT hills, no rocks are 
known to occur for a considerable distance, but the syenite hills of Hagai- Parkar, which are 
in this direction, may probably belong to tlie Malani series. To the eastward of Balmir no 
rooks are seen for 30 miles, but the porphyritio felsites are extensively developed on the Lnni 
river for many miles below Jasol and Panehbhadra; they appear to form a portion at least 
of the high hills south-west of Jasol, towards Jailor, they constitute the few rocky bills 
which rise out of the sandy plain between PancUibsdra and Jodhpur, and they reappear at 
Jodhpur itself, where some of the beds are unmistakable volcanic ash. On the road from 
Jodhpur to Jesalmir, their presence, except near Jodhpur, was only detected in the neighbour¬ 
hood of Pokran. 
2. Shales of Lowo and Pokran .—The next series of beds in ascending order consists 
of peculiar green, red, and variously coloured shales, occasionally soft, but often hard and 
even porcellanic. Some are fine, others are coarse and sandy, and contain grains of pink 
felspar, and of a green mineral resembling epidote; some beds being composed throughout 
of one or the other of these minerals. In places, pebbles and boulders of the Malani por¬ 
phyries and syenite are found towards the base of these shales ; the boulders being occasionally 
