OP THE MALYEEN HILLS. 



515 



Mr. Teall said that Mr. Rntley had described a number of im- 

 portant facts, but was very guarded in his interpretation of them. 

 Dr. Callaway offered solutions of many of the problems. The pas- 

 sage from felsite into a variety of mica-schist was of great interest. 

 He agreed with Dr. Callaway, that crystalline schists and massive 

 igneous rocks of similar chemical composition are frequently found 

 in association with each other. He also agreed with Dr. Callaway 

 as to the origin of certain banded gneisses. Granitic and dioritic 

 rocks might be seen in one part of the Lizard to vein each other in 

 the most intricate manner. It was possible to trace the veined 

 series into a banded gneissic series without a break. He regarded 

 the banded gneissic series as the result of the deformation of a 

 complex mass of plutonic igneous rock, and this was the view he 

 understood Dr. Callaway to maintain with reference to some of the 

 Malvern gneisses. 



Dr. Hicks said that the two views were nearer than would appear. 

 Each admitted that there was a granitoid rock in the centre, with 

 dioritic rocks on the flanks, both igneous. To a certain extent these 

 conditions are similar to what is found in some parts of Scotland, 

 where, associated with granitoid rocks, there is a series of schists and 

 gneiss. He was disposed to incline towards Mr. Hutley's view, that 

 there is a series of some kind, probably as in the Pebidian — a vol- 

 canic series — where pressure had produced schistosity in parts 

 even of the intrusive rocks, but not in the great masses. Dr. 

 Callaway speaks of a felsitic rock converted into mica-schist ; from 

 this view he was inclined to differ, as some of the specimens exhi- 

 bited as converted into mica-schists should be classed rather as 

 schistose felsites, as the felsitic structure is not destroyed, and the 

 mica occurs as a secondary product along the cleavage-planes, mainly 

 as the result of infiltration. The Archaean rocks may be, in the 

 main, of igneous origin, but they contain also detrital and chemical 

 deposits. 



Col. McMahon asked Dr. Callaway whether the foliation e of a 

 certain mass shown on one of the diagrams had been produc d by 

 intrusion, by pressure previous to consolidation, or by pressure sub- 

 sequent to consolidation, and, if subsequent, how he accounted for 

 the granite showing no foliation at all. 



Dr. Callaway expressed himself unable to explain Mr. Eutley's 

 diagrams, and 



Mr. Rutley stated that the section through the North Hill was 

 hypothetical. 



The Pkesident commented on the different inferences drawn from 

 the same set of facts. In the North Hill there are rocks not foliated 

 and others greatly foliated. To Mr. Rutley this afforded the 

 strongest proof of difference of origin, whilst Dr. Callaway saw 

 gradual transitions from one to the other. The attempt to explain 

 the formation of schists from volcanic rocks of an acid character 

 had not been made before in this country. 



Mr. Rtttley, in reply, was at a loss to recognize the position of 

 Dr. Callaway's section. He remarked that the foliation in these 



