SILHET TRAP^ 37 



most earthy and ash-like forms of the eruptive rock. The littlte ridge of 

 the Tarna spur is formed of metamorphics ; and I found an excellent 

 section of the earthy trap resting on the quartzites. On descending 

 northwards from here to the river under Nongriath and ascending 

 again hy the spur west of Mamluh none but metamorphie rocks are 

 seen, with some strong bands of dense dioritio rocks associated with 

 them. On descending the Tarna spur westwards by the path to Ramdai 

 one crosses a small patch of the earthy trap at about half-way down ; 

 but with this exception the metamorphie rocks last the whole way to 

 the village. The stratified trap appears again just to the west of 

 Ramdai and continues for the whole way over the spur to Tenrong ; it 

 is evident, however, that the cKffs to the north must be supported on the 

 metamorphics, for the debris of these rocks is abundant all along the 

 path. Again we find the outer ridge of the Tenrong spur to be of 

 metamorphics, and they last the whole way down to the Bogapani. Close 

 above the river there are numerous symptoms of the Silhet trap, and in 

 the rocks exposed in the bed and banks of the torrent there is a grand 

 display of the trap cutting through the quartzose schists, in a perfect 

 net-work of veins. I was so pressed for time that I could not attempt 

 the difficult work of following down the section to the junction of the 

 main trap, which I imagine not to be far off; but I have no doubt that 

 these veins belong to the Silhet trap ; they are quite unlike anything 

 I have seen in the older trap. Unfortunately the rainy season set 

 in before I could follow up my investigations of these interesting 

 sections. / - 



The section described in the last paragraph, from below Mamluh 

 due west to the Bogapani, is exactly on the run of the boundary in the 

 glens to the east ; but it shows conclusively that the junction is in no 

 manner a faulted one, and that the trap was piled up against a pre- 

 cipitous face of the metamorphie series. The section in the Bogapani 

 below Tenrong is a more complete case of what was observed at the 



z ( 187 ) 



