OP THE MALVEKX HILLS. 



513 



Fig. 10. Diorite. Swinyard's Hill, north side of highest point of ridge. X 18. 

 (Specimen 25.) 



11. Biotite-muscovite-gneiss. Swinyard's Hill, largest quarry, south end. 



X 18. (Specimen 27.) 



12. Mica-schist. Eaggedstone Hill, east spur, top of north end. X 18. 

 (Specimen 28.) 



Plate XXI. 



Fig. 1. Altered felspathic sandstone. Eaggedstone Hill, top, east spur. X 25. 

 nicols +. (Specimen 30.) 



2. Quartzite-schist (micaceous). Eaggedstone Hill, top, east spur. X 25. 



(Specimen 31.) 



3. Microciine-crystal (crushed and faulted) in granitic vein. Quarry close 



to and on south-west of the Wych. X 35, nicols +. (Specimen 

 33.) 



4 & 5. Corroded and bent crystals of triclinic felspar in basalt. Here- 

 fordshire Beacon, east side, at back of the cave (see also fig. 9, PI. XX.). 

 X 55, nicols +. (Specimen 19.) 



6. Grlobulitic crystallites in biotite of granite. Worcestershire Beacon, 



north side, near summit. X 850. (Specimen 12.) 



7. Devitrified obsidian, showing perlitic structure and faulted band. 



Herefordshire Beacon, back of the cave, overlooking Castle Morton 

 Common. X 55. (Specimen 20.) 



8. Diagram showing track of spontaneously moving bubble in fluid-lacuna 



in quartz of gneissic quartz-syenite. North Hill. (Specimen 1.) 



9. Group of apatite crystals in diorite. North Hill, just south of Ivy 



Scar Eock. x 350. (Specimen 7.) 



Note. — When not otherwise specified, the figures are represented 

 as viewed by ordinary transmitted light. 



Discussion 

 (December 1, 1886). 



The Pkesident said that it was satisfactory that the Author had 

 been able so completely to confirm Dr. Holl's work. The three 

 issues raised in the paper would probably meet with a varying 

 amount of acquiescence on the part of the members : — (1) that 

 these rocks are metamorphic, and not igneous, few would contest ; 

 (2) there might be a difference of opinion as to the significance of 

 the apparent succession ; (3) he anticipated a debate on the relation 

 of foliation to sedimentation. 



Prof. Bonkey would abstain at so late an hour from discussing 

 the general question of foliation. Some years ago he had made a 

 collection of these rocks, as also had Mr. Allport, who, he trusted, 

 would yet publish the results of his investigation. He would now 

 only ask : — 



(1) Had the Author detected any indications of schistosity along 

 planes of mineral banding ? 



(2) Is there any strong proof of mechanical disturbance productive 

 of cleavage-foliation ? 



(3) Lastly, in studying the structure of the more coarsely crys- 

 talline rocks, had he come upon those curious structures which occur 

 in the oldest known gneisses, or upon those distinctly characteristic 



