1809.] features of the Jaintia hills. 155 



the trap rock comes in with the fall in the country, and the high 

 isolated peaks to the south of the Mangkhen are found to he a con- 

 tinuation of the quartzitic sandstones of the Shillong peak, &c, almost 

 perpendicular, but lying up against an amygdaloid trap, associated 

 with a true granite which comes in with an east and west run on 

 the north, and forms the remarkable rounded bosses, such as Billu 

 Kongor, &c. Granite also occurs contiguous to the gneiss north of 

 Nartiang, and thence in an easterly direction immediately north 

 of Nongjinghi which is almost the highest point of the Jaintia hills, 

 4,563 feet above sea level. The Nongjinghi ridge is gneiss, resting 

 against the granite. As at Lailangkote in the Khasia hills, the trap 

 is closely associated with the granite, and in such situations the 

 titaniferous iron sand is found in great quantity, and smelting fur- 

 naces are seen in all the adjacent villages. This dark green trap 

 appears to have been injected between the granite and gneiss, or be- 

 tween the former and the quartzitic sandstones at or about the period 

 of the great disturbance and change in the metamorphic series. The 

 parallelism of the drainage lines south-east of Jawai, is very remark- 

 able, and with the cross-drainage at right angles breaks the country 

 up into irregular parallelograms, which probably display a monster 

 jointing of these metamorphic rocks. 



The most remarkable lines taken up in succession by different great 

 valleys and ravines are — 1st, a main line, rather irregular, but to which 

 all lines to the south conform, commencing on the west at Karpenter 

 village on the Mangat ; that river carries it to Jarain, E. N. E., up to 

 the junction of the Kawa Manvi with the Mantadu, north-westerly 

 by the Keremontha ravine past Wapung into the IJmpa-ai and by the 

 Murin into the Kopili near Thelgasi ; this last river continuing on for 

 many miles with a north-east course, altogether constituting a great 

 physical feature extending from west to east for 55 miles. The 2nd 

 line, at an average distance on the south of 6 miles, can be traced 

 from Pomtadong, past Thangbuli, to the Mantadu river at the junc- 

 tion of the Baliang, on the left bank, following this last named river, 

 over the watershed into the Lonnang river, and in succession by the 

 Umkorpong to the north of Satunga, where this river turns sharp 

 at right angles to the south. Yet the same direction can be carried 

 on to Umthnong, and is lost in the sudden W. S. W. bend of the 

 Kopili. 



