Chap. VIII. ] trap dykes and intrusions. 143 



number of the principal faults, those faults having been in all cases 

 where intersection has been observed of older age than the trap. Many 

 apparent cases of trap dykes being faulted arise simply from the crack 

 which they have filled having split somewhat irregularly in that place, 

 as in the accompanying diagram, Fig. 9. There is a case close to 

 the village of Amkula, West of Raniganj, where a dyke is thrown 120 

 feet in this manner without any fault. 



Fig. 9. Dyke thrown without a fault near Bonoha. 



'>'■_ ' - V <T 





It is also possible that the Salma dyke, and a few other large dykes, 

 lying West of it, and parallel with it, and' which are composed of a 

 very compact trap, often finely columnar, may be of a different age 

 from the smaller dykes ; but there is no proof of such being the case. 

 Relatively to each other, there can be no question that some dykes 

 preceded others. There are very many cases where a newer dyke is 

 seen to cut an older one. This may be observed in numerous instances 

 in the country immediately West of Raniganj, and nowhere better 

 than in the two parallel dykes which pass through the colliery, and 

 separate the old abandoned mine from the new one now worked. One 

 of these is seen to cut across the other four or five times at least, and 

 affords an interesting example of a second dyke following approximately 

 the same general line of weakness which a former one had taken. But 

 there is no evidence that this difference of relative age implies a differ- 

 ence of Geological Epochs. Just as in any volcano, where a section is 

 exposed, some dykes may be seen cutting others, and yet all may have 

 been formed within very few years of each other, and the whole mass 



