MAKTTM FIELD. 45 



Considering that in not one of the above sections (except of the 

 minor seams of 7 and 4 feet ) is the full thickness of the coal visible, 

 it can hardly be above the mark to take the average thickness of the 

 coal at 10 yards. With regard to the breadth of the workable fringe, 

 we have, in some places, a local dip of the seams towards the north, 

 which, if constant for any distance, would enable the coal to be advan- 

 tageously followed into the hills towards the ' rise .' Elsewhere, again, 

 the outcrops are several hundred feet above the plain, and faci- 

 lities would probably present themselves for adit workings. But 

 frequently it would be necessary to mine towards the deep. Taking 

 it all round, then, the seams could probably be worked without 

 any serious difficulty to a distance of 200 yards from the surface 

 (measured along the seam) . With an average dip of 40°, this would 

 involve a vertical depth from the outcrop of less than 400 feet in the 

 most unfavorable case of working towards the deep. This cannot be 

 regarded as excessive even in Assam, considering that some of the 

 E,aniganj mines, where the low dip of the coal renders deep mining as 

 yet unnecessary, have reached 250 feet, and that in Europe pits have 

 been sunk to as much as 3,000. The distance, then, from the Tirap 

 quarries to the Namdang being 5g- miles, the cubic contents of the 

 available known coal on the above estimate is h\ x 1,760 X 200 X 10 

 yards, containing over 18 million tons. Considering the difficulty of 

 working such very thick and such highly inclined seams, a liberal allow- 

 ance must be made for loss in mining. If this be taken at one-half, 

 there remain nine million tons of marketable coal easily procurable. 



In the above estimate no account is taken of other seams, which 

 there can be no doubt exist, beside those already known, nor of the ex- 

 tension of the field itself to the west and east. These figures must 

 therefore be taken as the smallest quantity that can reasonably be ex- 

 pected, but there are not sufficient data to estimate how much more 

 may be anticipated. 



( 313 ) 



