KHASI HILLS. 193 



its thickness as " above 20 or 30 feet"( a ). This great difference in 

 statement no doubt arises, in a great degree, from the extreme looseness 

 with which such assertions are commonly made, as when a bed of coal 

 is stated to be of " 20 or 30 feet" in thickness ( a difference in thickness 

 of 10 feet being apparently considered perfectly immaterial), but I am 

 inclined to think that, in the present case, it has in some degree arisen 

 from another circumstance to which I have referred above, namely 

 that at the part of the hill in which this coal was first examined there 

 is a fault ( or rather two or three small step faults combined ) which 

 have an up-throw to the West of about 40 feet. It would be very easy 

 to be led astray in estimating the total thickness of the coal in this im- 

 mediate spot : and it is I think very probable that some of the ob- 

 servers measured the distance between the bottom of the coal on one 

 side of these disturbances, and the top at the other side. A o-lance 

 at the accompanying Sketch will explain this, (f'-ig. 19/ Although not 

 intended to represent the exact conditions of the case, this figure will 

 show the possibility of being misled in a hasty examination. 



— ^W7 



Fig 19. 



The bed of coal is here represented as broken up and dislocated 

 by four small faults, which are all up-throws to the West. If then 

 this portion of the section were partially concealed by fallen detritus, 

 it •would be very likely that the space between a and b would appear 



(a) Proceedings of the Geological Society, London, Vol. IL p. 567, June 14, 1837. 



