382 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 4, 



5. On Trap-dykes intersecting Syenite in the Malvern Hills, 

 Worcestershire. By the Rev. W. S. Symonds, F.G.S. 



Among the varied phsenomena described and registered respecting 

 the Malvern Hills in Prof. Phillips's admirable work in the * Memoirs 

 of the Geological Survey of Great Britain ' (vol. ii. part I), I am not 

 aware of any notice of the effect of injected and intersecting trap 

 upon the syenite of which the great mass of the Malverns is com- 

 posed. 



I had for some time been aware that greenstone and trap-dykes 

 traversed syenite in a quarry worked between the Winds-point and 

 the Obelisk, and to which last autumn I directed the attention of 

 Mr. C. J. Fox Bunbury. Having been requested by Sir W. Jar- 

 dine to examine the site of the great Malvern bonfire of January 

 last, in order to discover whether any signs of the vitrification of the 

 rocks were visible, I did so, and was immediately struck with the 

 appearance of the roasted syenite which formed the platform, and 

 the similarity presented by the baked mineral to syenite in contact 

 with dykes of trap and greenstone at the quarry at the back of News 

 Wood, half-way between Winds-point and the Obelisk. 



I was accompanied during this investigation by a Swiss geologist. 

 Dr. De la Harpe, well accustomed to metamorphic phsenomena ; he 

 was much struck with this most interesting quarry. 



I may here mention that a high wind prevented the flames of the 

 Beacon fire ascending to any height, and I was informed by those 

 present that an intense glow was concentrated upon the syenitic 

 platform. 



At the quarry in question several dykes traverse and alter the 

 syenite, and the metamorphism presented by the rock in contact 

 with the greenstone is nearly identical with the effect produced by 

 the Malvern fire. 



One of the dykes runs nearly north and south, and is about 10 ft. 

 thick, another from east to west ; while a third, of a different kind 

 of trap, traverses from north-east to south-west. 



The syenite is altered for several feet from its contact with the 

 dykes, and then gradually assumes its crystalline form. 



I have traced the dyke running from north to south to a consider- 

 able distance, and at the Gullet Pass it traverses the Holly Bush 

 sandstone, metamorphosing that rock into a steatitic gneiss. 



At the valley of the White-leaved Oak, trap is again seen in contact 

 with Holly Bush sandstone, and there also changes it into a gneissose 

 schist. I am inclined to attribute this effect to a prolongation of 

 the same dyke in a southward extension, and I think that the infil- 

 tration of the trap took place before the upheaval of the syenite, 

 but after that rock was consolidated. 



