26 BOKARO COAL-FIELD. 



A large dyke crosses the river as represented on tlie map. It is 

 traceable south of the Koonar, but is not visible in the Damoodah, 

 which is somewhat extraordinary^ as it is by no means a small one. 



Opposite the villages of Jereedeeh and Jerungdeeh coal is again seen, 



but dipping west. It is nearly destroyed by per- 

 Coal near Jereedeeh. . 



meation or trap throughout it. Jbrom this seam 



some fine specimens, illustrating the occurrence of the trap, were obtained. 

 The plan resembles a series of irregular quadrangles. These are produced 

 by injections of trappean matter, which filled up numberless cracks of 

 shrinkage more or less at right angles to each other. These cracks 

 occurred along the structural lines so common in coal, hence their regu- 

 larity ; for if they were due merely to the forcible passage of trap 

 through the mass of heated coal, they would present a much more 

 unsystematic pattern than they do. 



A seam on the south bank of the Damoodah, through which the 

 Foosro dyke passes, afibrds some very good samples of trap-afiected coal. 

 The quadrangular structure is rendered very prominent by the contrast 

 in colour of the black carbon and light yellowish grey of the weathered 

 trap ; and from the superior hardness of the latter, it generally projects 

 above the surface of the coal. 



At the mouth of the Koonar there is a sharp anticlinal. 



Coal South-Uast of Jereedeeh.-— K seam is seen south-east of Jeree- 

 deeh in the fields bordering upon the Damoodah. 



The dip near the southern boundary becomes reversed, and it is 



evident that as hitherto we have had a regular 

 Reverse Dip. 



succession of strata dijDping southwards whose • 



thickness far exceeds that of the reversed beds, there must be a fault in 



the neighbourhood; whether forming the limit of the field or not 



depends upon the extent of denudation which the country has sufiered 



posterior to its formation. 



(64) 



