CHAP. 4.] KADAPAH FORMATION.—NULLAMULLAY BEDS. 229 
given) show how the quartzites underlying the same series in the northern 
part of the Yellacondas are likewise much folded. 
It is a feature in the Cumbums that bands of quartzites of greater 
Intercalated bands of OF less thickness are more frequently intercalated 
quartzite. than in any other of the slate groups. These 
are very often confusing, on account of their general resemblance to one | 
another and to other quartzite runs; it being difficult, if not impossi- 
ble, to say whether they really belong to the slates or to a superin- 
cumbent series. 
The wide superficial display and the average dip of these slates sug- 
aaar ui ui gests an enormous thickness; but this is to some 
extent deceptive, owing to the undulatory lie over 
the wider areas. Taking the section (No. 1, Plate IX,) just south of 
Porenaumla, there must be a thickness of over 3,000 feet ; and below that 
part of the Byrenconda which is capped by Irlaconda quartzites, there 
are again 9,000 feet. These are, perhaps, about the safest thicknesses 
taken in the eastern field, as representing them at their deepest, for they 
thin out a good deal to the north and north-east. 
The slates are of all varieties from fine silvery talcose beds, through 
A MM TERM coarse grey, purple, and blue slates, to grey and 
` reddish-brown earthy clay-slates. They are occa- 
sionally foliated and schistose, often not to be distinguished from the 
schistose crystallines alongside of them. It is quite impossible to say 
in numerous localities how these different varieties occur with regard 
to each other, except when there are good continuous outcrops; while 
the cleavage is so strong that quite a magnified idea of the thickness 
of the beds may be produced on the mind of the observer. 
Along the base of the western slope of the Yellacondas the strata 
are dark-green taleose and chloritie slates, almost schistose, weathering: 
generally of a dark rusty-brown color. Below these, as in the Budvail 
and Porenaumla belt, they are pale-brown and reddish, streaked, 
(229) 
