NERBUDDA DISTRICT. 173 



Again, among the Talcheer beds trap dykes are very frequently 



seen ; and the same considerations as those just 

 Also by Trap Dykes. , 



now offered seem here also to be applicable. 



Those dykes which have been noticed among the clearly bedded rocks 

 are sometimes, though not universally, seen to produce violent dis- 

 ruption of the masses among which they have been forced ; and there 

 seems to be no reason why similar dykes among the amorphous Tal- 

 cheer should not have been accompanied by similar mechanical 

 violence. Still little definite can be said of the movements, which 

 have there been shewn by analogy, to have probably affected the 

 Talcheer. 



With reference to the lower Damudas, whose flags, shales, and sandstones 

 afford means of observing the results of any disturbances which may 

 have affected them, we have already mentioned the breccia lines, and the 

 trap dykes, in connection with the indications of mechanical violence. 

 It has been found that the former are much more coincident with lines 

 and areas of disturbance than the latter. 



In many cases it has doubtless occurred that a trap dyke marks the 



m , , -, . i, line along which beds have been twisted and brok- 

 Trap dykes dynamically & 



considered. ellj an( j }j as sometimes perhaps been itself imme- 



diately connected with the active cause of ruptures and contortions. 

 This is suggested when we find the igneous rock filling in cracks, and 

 fissures, of the sedimentary rock, along a dyke line, and enclosing frag- 

 ments of it; but evidence of great disturbance among the bedded rocks 

 by no means generally coincides with great development of igneous action ; 

 and Fig. 6 (p. 63) shows a case where intrusive trap has exercised or 

 been accompanied by little or no disturbing influence on the flags and 



Areas of maximum sliales about lt Tnere are indeed traceable in the 

 disturbance. district, areas of maximum disturbance, but these 



coincide, not with the areas of maximum igneous action, but with the 

 ooundaries of the formation, and it is also near those boundaries that the 



