88 mallet: coal-fields oe the naga hills. 



Petroleum. 



The intimate connection of the Assam petroleum with the coal 

 measures is too obvious to escape attention. Altogether, the oil is known 

 to rise in contiderably more than a dozen localities, every one of which 

 is either on, or close to, the outcrop of the coal-bearing group. With 

 the exception of the Janji, petroleum has been found in every coal-field 

 from the Namrup to the Disai, and there is no recorded instance, that 

 I am aware of, of its occurrence elsewhere in Upper Assam. In the 

 majority of cases the springs are near the outcrop of one or more seams 

 of coal, and in one instance I have seen the oil oozing out of the coal 

 itself. This, however, may possibly have been accidental, the coal being 

 merely the last rock through which the oil passed on its way to the 

 surface. But, on the other hand, there is reason to believe that a very 

 moderate heat, such as would be afforded by the natural temperature 

 of the ground near the surface and the chemical action involved in 

 the process, is sufficient for the production of petroleum under certain 

 conditions. 



Marsh gas is a frequent accompaniment of the oil, and there may 

 also be a connection between the latter and the saline springs which 

 were formerly utilized by the Assamese for the production of salt, at 

 Borhat, Jaipur and elsewhere. The association of petroleum and salt 

 or saline springs is very common. In India it has been observed both 

 in Burmah'^ and the Punjab,t although Mr. Theobald is of opinion that 

 the co-existence of the two in the former province is merely fortuitous. 



It was clearly shown by the results of Mr. Goodenough's attempt to 

 bring the petroleum into the market % that the supply is abundant near 

 Makum; and it is not unreasonable to hope that it will be found 

 equally large further west. In the Dikhu valley the conditions most 



* Records, Geological Survey of India, Vol. VI, p. 70. 



t Memoirs, Geological Survey of India, Vol. XI, pt. 2, p. 25. 



% P- 11- 



( 356 ) 



