Chap. IY. 1.] metamopxPihc rocks. 85, 



2nd. — The fine scarp at edge of the northern platean basin of the 

 KolymuUays close to Perracnrrah, is due to the strong- development of 

 two joints which cross each other nearly at right angles. One runs 

 north -north-west, south-south-east ; the other north-east Ly 5° — 6° east, 

 south-west by 5°--» 6° west. 



3rd. — The western edge of the western part of the Patchamullaj^s 

 shows a remarkable (see page 16) and very sharply defined scarp, running 

 due north and south, Avhich appears to be entirely due to the north and 

 south joints, which are extensively developed in that part of the country. 

 The sedimentary origin of the gneiss, as far as true bedding offers 

 Sedimentary origin of ^^7 W^of, is very apparent in many localities. In 

 ^^ ^"^'^^' the southern part of the area, as in the country 



around TuUamullay hill, Thathengarpaittai, and Toriore, in connection 

 with the magnetic iron beds running from TuUamullay into the Koly- 

 muUays, such a structure is very well exemplified. Beds of hornblende 

 rock, quartzose gneiss, (occasionally false-bedded,) and hornblende schist 

 dipping at various angles, are easily traceable for miles across the level 

 country as streaks of pale and dark rock, as well as on the faces of a few 



sharp ridges and conical hills. TuUamullay is com- 

 TuUamullay. "^ 



posed of highly inclined beds, the hardest of which 



run up to form the precipitous peaks which render the hill so characteristic 



from all sides of the country. Between TuUamullay and the KolymuUays 



there is a low mass of ridged hills just north-east of Mahdavy, which on 



examination shows a structure almost as distinctly 



Mahdavy hills. -^ 



marked as are the different beds shown in the ac- 

 companying sketch section Fig. 5. 



Fig. 5.— Sketch section of Mahdavy Hii,l. 



m. 



1\ r, Ilornblcndk beds: /, ', niagiitlic ii-un: y, 5, Quartzosc gneiss. 



.307 ) 



