Pt. II. Chap. II. ] collieries — mode of working. 175 



in course of time, the seams near the surface being exhausted, it 

 may become necessary to sink pits to a greater depth. When this 

 occurs, the increased expenditure for sinking pits will induce proprie- 

 tors to work a larger area from a single pit, or pair of pits, than they 

 now do. 



This will produce a considerable change in the circumstances attend- 

 ing the collieries. At present the ventilation is entirely natural, and 

 the large number of pits renders it, in general, very good, but with 



greater depth, the necessity for good ventilation 

 Ventilation. 



will increase, especially if fire-damp occurs. If, 



under these circumstances, the means of natural ventilation are not 

 increased, (and they will, doubtless, on the other hand, be diminished), 

 it will be necessary, both for the health of the miners, and the safety 

 of the mine, to have recourse to some of the artificial methods for 

 passing a current of air through, the workings, which are employed 

 in European collieries. 



The liability of the coal of the Damuda field to spontaneous 

 Drawbacks. combustion is probably the greatest drawback 



Spontaneous combus- whicn exists to its universal employment; other- 

 wise its comparative cheapness would, in a great 

 measure, compensate for its disadvantages in competing with English 

 coal even for marine purposes. It was, for many years, the practice 

 in the various collieries around Raniganj, to leave the small coal, 

 which was, at that time, quite unsaleable, in the mine, and several 

 fires were the result. An account of the conflagration which necessi- 

 tated the abandonment of the former mine at 



Eemoval of smalt coal. . ..-,«»„ mi i c t • -ir tttmt , 



Raniganj, m 1842, will be round m Mr. Williams s 



Report. A portion of the Mangalptir mine has also been on fire, and 



the same is the case at Chokidanga, and, probably, at some other mines, 



in abandoned portions of the workings. An attempt to use small 



coal as "stoppings" to produce artificial ventilation, once caused great 



