514 



ME. E. RUTLEY ON" THE ROCKS 



of igneous rocks, and were they in any way modified by meta- 

 morphism ? 



If these Malvernian rocks are gneisses of true Laurentian types, 

 he would find them exhibit certain modifications in passing upwards. 



Mr. Teall said that the Author had described a number of facts 

 which any theory of the district would have to account for. What 

 is the significance of the principal structural planes ? This was the 

 question which must be solved before any advance in the theoretical 

 interpretation of the district could be made. The Author appeared 

 inclined to think that these planes were originally planes of strati- 

 fication ; otherwise no conclusions as to age could be drawn. The 

 coarsely crystalline rocks were igneous rather than sedimentary in 

 aspect. He thought they might be igneous and of plutonic origin. 



The President observed that both the great longitudinal fault 

 and also the cross faults were of later date than the foliation. 



The Author, in reply, said that the President had indicated with 

 great clearness the lines which the discussion should take. He 

 agreed with him concerning the age of the faults ; the amount of 

 their throw is difficult to determine. Had he known of the in- 

 tention of Prof. Bonney and Mr. Allport to take up this subject he 

 would have abstained from the task. . Not having fully examined 

 bis slides, he was unable to answer questions relating to the micro- 

 scopic characters of the rocks. He had found no particular evidence 

 of mineral reconstruction along divisional planes. Difficult to say 

 whether these rocks were or were not igneous ; they are very like 

 some igneous rocks and yet with a rude foliation. He then spoke 

 of the different meanings attached to the word metamorphism. 

 Judging from hand specimens, the Malvern rocks seemed to resemble 

 those from the Hebrides and Canada. He had little doubt that 

 the fine-grained schists were sedimentary, as they even contained 

 beds of quartzite. He admitted that, according to the meaning 

 given to the section, the great planes must be taken as bedding- 

 planes. If the rocks were igneous, then the divisions into upper, 

 middle, and lower groups had but little meaning. There may have 

 been interbedded lava-flows. He had never met with divisional 

 planes of such an even and persistent character in undoubted 

 plutonic rocks. The divisional planes, rudely parallel to the sur- 

 faces of granitic masses, such as those described by Boase and 

 De la Beche, were far less regular. 



Discussion - 

 (April 6, 1887*). 



The President observed that the Society did not often enjoy the 

 advantage which they had that evening, of hearing papers on the 

 same locality by two authors who looked at the subject from dif- 

 ferent points of view. 



* This Discussion relates also to Dr. Callaway's papers on the Kocks of 

 Galway and the Malvern Hills, pp. 517 and 525. 



