GNEISSIC KOCKS. 13 



well also in a picturesque rocky hill north of Ambalathandi (of map) a 

 village 4 miles west of Madura, and again in some low rocky hills 6 

 miles further to the north-west close to the Sholavandan-Tirumaii- 

 galam road. It is largely quarried in the Sikandar Malai, the pinkish 

 grey well-banded rock yielding a very handsome and durable building- 

 stone. The bedding is not distinctly seen except from a distance, but 

 is very striking when viewed from the south-east. 



4. The middle granular quartz rock group forms the long and 



important ridge called the Nagamalai (already 

 Middle granular quartz 



rock, or Nagamalai referred to Several times), which for many miles 

 forms the southern side of the Vaigai valley, but 

 dies down under the alluvium 4 miles west-north-west of Madura city. 

 The beds make a great curve south-eastward under the alluvium and 

 re-appear in the Pasumalai (or cow hill), a low bare stony hill to the 

 north of the Sikandar Malai. From these the beds strike east-south-east 

 for 2 or 3 miles and then disappear under the alluvium. These beds were 

 followed up north-westward to the point 20 miles distant from Madura 

 at which the Nagamalai changes its course and trends east by north to 

 west by south. Their further extension south-westward is not yet known 

 geologically. The eastern extension beyond the Vaigai will be described 

 further on. The dip of these extremely coarse granular beds is much 

 obscured by excessive jointing, but it is unquestionably northerly or 

 easterly according to the strike of the beds and at very high angles. 

 Some of the basset edges at the east end of the Nagamalai are wea- 

 thered into bold tors, many of which present considerable resemblance to 

 buildings and are often mistaken for ruins by travellers along the railway. 

 Except where the mass is much broken down by weather action, the 

 ridges of this peculiar rock are remarkable for their extreme barrenness 

 of vegetation of all kinds. Owing to their very light colour, which 

 varies from extremely pale reddish-white to pale reddish, or yellowish- 

 drab, they show conspicuously to great distances. To the south-east 

 of Madura a group of beds of identical character, which can only be 

 regarded as the easterly extension of the Nagamalai beds, appears on the 



( 13 ) 



