354 THE MURCHISONITE BEDS OF THE ESTTJARY OE THE EX. 



West Somerset, and that there were signs of fanlts, just as the 

 cliff-sections show many faults by which the beds are repeated. 

 He understood that the derived Murchisonite does not occur in the 

 lowest bed, in which there is a large quantity of limestone frag- 

 ments. He inquired whether the Murchisonite came from the 

 granite of Dartmoor. 



Mr. Evans remarked that there was much interest in the question 

 whether the materials of the beds described were derived from gra- 

 nites at no great distance. The composition and structure of the 

 crystals should be compared with those of the Dartmoor crystals. 

 The peculiar appearance of iridescence on the cleavage-planes might, 

 he thought, possibly be due to internal decomposition. 



Mr. Ormerod, in reply, said that there could be no doubt that 

 the crystals of Murchisonite came from Dartmoor. Some specimens 

 are associated with schorl and tin; and some few specimens of Dart- 

 moor granite contain Murchisonite. He had not experimented on 

 the derived crystals ; but certainly some of their changes must be 

 due to their being buried in the Red Sandstone. 



