CHAP. 1.[ THE KADAPAH FORMATION. 143 
| and are not sufficiently cleaved to split in other planes than those of depo- 
sition. The long ridge of hills just inside the Yellaconda, and stretching 
northwards from the Budvail ridge of the Cuddapah district past 
Poremaumla, is largely made up of flagey quartzites; while, on the 
other hand, the western flank of the northern end of Rajpollam ridge 
(about twelve miles south-south-west of Cumbum), is almost entirely of 
` quartzose slates, or slaty quartzites. 
One reason for separating this series into so many groups of sands 
, and slates is the fact that it, especially in the 
Slates and quartzite 
bands suggest natural Nullamullays, is made up generally of such 
grouping of zones. pr 1 
distinct bands of quartzites and slates. The 
lower groups, as they are developed along the western side of the area, 
are very easily settled ; for here there are groups of strata which are 
distinetly separated by overlap and unconformity. 
In the Nullamullays, there are no other strata but those of quart- 
zite and slates, and, consequently, it is very difficult to recognize the 
same bands again if there be anything of a large gap in the continuity 
of their outcrop. This outcrop is fortunately tolerably clear along the 
slopes of the mountains, so that the boundaries are followed out without 
much difficulty. 
It must not be understood, however, that the different bands of 
quartzite and slate are made up simply of these different rocks; only 
that they are more slaty in their general character, or more of quartzites. 
There are bands of quartzite beds in the slate groups, and vice versd ; 
and, perhaps, as a general rule, the quartzite groups contain finer and 
thinner bands of slates than the slates do of quartzites. It is also not 
anfrequent that, as the different groups are traced out, they sometimes 
lose their distinctive character as of one kind of rock or the other, 
quartzites being replaced by slates; though, perhaps, it would be 
nearer the truth to suppose that a group has thinned out altogether 
at times. 
) 0 
