462 Dr. Irving— The Malccm Crystallines. 



•with a phyllolithic structure are cut through in the Wych Pass ; and 

 they appear to have been localised by slight faulting. But by far 

 the best example seen is in the quarry just north of the old pumping- 

 station at North Malvern, to which the proprietor directed the 

 writer's attention, as a case of a " blue marl " among the ci-ystalline 

 rocks. An inspection soon revealed the fact that the highly basic 

 rock had been crushed here against a massive multiple vein of 

 quartz, the most powerful develoj^ment of vein-quartz observed in 

 the whole range. The quartz-vein was itself extensively fractured, 

 and the chlorite, as a fine powder, had worked its way into the 

 fissures ; but the two minerals remained completely individualized 

 and distinct, showing no apparent tendency to enter into new 

 chemical relationships under even the intense pressure to which the 

 mass here had been subjected. This observation was repeated several 

 times, after being first made in the eaidy part of one's investigation ; 

 and reflection upon the extreme extent to which a hornblendic mass 

 had thus undergone deformation (where, owing to the great power 

 of resistance of the quartz-vein, conditions were exceptionally favour- 

 able to local concentration of mechanical force), threw much light 

 upon many facts subsequently observed in other parts of the range, 

 and served as the clue to some of the explanations which have been 

 ventured upon in the present paper. 



Repeated observations of the Malvern Crystallines tend to force 

 npnn the mind the idea that rocks rich in hornblende, or almost 

 entirely composed of that mineral, yield far more to pressure icitJiout 

 crushing, than do the more felspathic portions, or even the dolerites. 

 Hence it seems to follow that, where the original rock was very 

 felspathic, either from the presence of more numerous felspathic 

 veins, or from the more abundant distribution of felspar (and in 

 some cases much quartz) through the rock, we get a brecciated 

 mass along a plane of thrust, instead of anything approaching to 

 schistosity. Examples of such are seen in the quarries at North 

 Malvern, and in the cutting on the Wych Road just outside the 

 quarry by Rock Villa. Again, in the same quarry-face (as at Little 

 Malvern and Wind's Point) the more massive diorites have apparently 

 undergone but slight deformation, while the thinner masses, which 

 alternate with the felspathic veins, have been degraded into a rock 

 with a more or less phyllolithic structure, in which chloritic material 

 is abundant as a degradatioti-product of the original hornblende. 



General Conclusions. 



1. The field-relations observed among the crystalline rocks of 

 the Malvern Chain point to the conclusion that for the most part 

 their petrological morphology originated in diagenetic paramorphism 

 and not in any subsequent metamorphism. 



2. As regards the structural features (including schistosity) these 

 have resulted to a large extent from the action of mechanical forces ; 

 such results being chiefly of a melataxic nature (as the author has 

 defined the meaning of the term elsewhere), exhibiting various phases 

 of deformation of the original crystallines, while the action of 



