154 MICA TRAP DYKES. 



The investigation may possibly lead to valuable scientific 

 results. I have already mentioned that the majority of the 

 rocks of these islands are of immense geological antiquity. 

 But in England there have been many outflows of igneous 

 matter down even to tertiary times. At present there is no 

 evidence of any such action in Guernsey or Jersey posterior 

 to the carboniferous age. But if any dyke could be discovered 

 which should traverse or pierce one of these Mica Traps it 

 must be itself of Post-Carboniferous age, and would afford an 

 evidence of a later disturbance. And thus it becomes of 

 much interest to discover, enumerate, and closely examine all 

 these Mica Trap dykes of the Channel Islands. 



