54 



MALLET : GEOLOGY OF DARJILING AND WESTERN DUARS. 



degree to surface weathering 1 . Hence no material improvement in the 

 firmness of the coal can be expected as the drift progresses, and there is 

 every reason to suppose that the seams everywhere will, like this one, 

 prove as crumbly in the interior as at the surface. 



The following assays made by Mr. Tween illustrate the com- 

 position of the coal; the specimens were first 

 dried at 212° :— 



Composition. 



Dabjxling-Dahuda coals. 



Free carbon. 



Volatile matter. 



Ash. 



Rakti naddi, 5' 6" seam 



Cart-road, 6' 0" seam 



Chirankhola naddi, 7' 0" seam 



Tmdharia ravine, 11' 0" seam 



Ravine south of Pankabari, 0' 9" seam 



79-3 

 74-1 

 69-6 

 66-3 

 64-0* 



7-6 



9-0 



52 



12-4 



11-8 



131 

 16-9 

 25-2 

 21-3 

 24-2 



Aveeaqe 



70-66 



9-20 



20-14 



The samples were all taken at the out-crop, within a foot or two of 

 the surface, but the coal seems to be little altered by exposure. The 

 following assays are of samples taken at intervals of 10 feet in the 

 Tindharia drift : — 



TlNDHABIA BAVINE, 11' 0" SEAM. 



Free carbon. 



Volatile matter. 



Ash. 



At surface 



66-3 



12-4 



21-3 



10 ft. from surface 



66-8 



11-4 



21-8 



20 „ 



67*5 



14-4 



181 



30 „ 



64-4 



10-4 



25-2 



The coal iu many seams has a brilliant sub-metallic lustre; in others 

 it is duller. The former variety is more friable than the latter. The 

 mineral is an ' anthracitic coal ; ' not a true anthracite, the volatile matter 



( 54 ) 



