86 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



The quartzo-felspatliic and granitic veins are abundant throughout 

 the range, especially at the northern extremity of Swinyards Hill, in 

 the Herefordshire Beacon, opposite Malvern Wells, and in the 

 "Worcestershire Beacon. Some of the larger veins are granitic in 

 part of their course. Usually, however, they contain but little 

 mica, and often it is altogether absent. They have a common 

 character in the red colour of their orthoclase-felspar, which in some 

 occurs in large eleavable masses ; in others the quartz and felspar 

 form a grantdar mixture, often minutely so. They traverse all the 

 rocks indifferently, with the exception of the traps, which are pos- 

 terior to them in date. 



The source of these veins is not very clear, unless we adopt Prof. 

 Dana's views as to their mode of formation*. 



The situations of the principal protrusions of trap, of which there 

 are upwards of forty, have been already indicated in the general 

 description of the rocks of the hills. These traps have everywhere a 

 very uniform lithological character, and consist of aluminous augite 

 and a felspar allied to labradorite, usually of a brownish colour f, 

 their relative proportions varying only within narrow limits. In 

 two of the dykes in the Terminal Hill, at the northern point of the 

 range, the rock contains, in addition, some iron in a low state of 

 oxidation. "Where most highly crystallized, as in the central por- 

 tions of the masses, the rock has a dotted appearance ; but nearer to 

 the margins it becomes fine-grained, and at the line of contact with 

 other rocks, and in the short prolongations some of these masses 

 send forth, it is always compact and homogeneous. 



These trap-rocks are all highly jointed, especially the more com- 

 pact portions, and break readily into small rhomboidal or cubical 

 fragments, so that fresh surfaces are often difficult to obtain. None 

 of the quartzo-felspathic or granitic veins which traverse the meta- 

 morphic rocks penetrate the trap masses; on the contrary they 

 always end against them abruptly, and in this respect the traps differ 

 from the dioritic rocks, in which such veins are more or less 

 abundant. The traps are, therefore, posterior in date to the veins. 

 They are anterior, however, to the elevation of the range, as may be 

 inferred from the brecciated appearance which they frequently pre- 

 sent, showing that they have partaken in its movements. "We may 

 infer it also from the impossibility of a chasm crossing a ridge being 

 filled to the summit with a fluid mass, which would necessarily flow 

 out at the base on either side. The brecciated structure has been 

 produced by the displacement of the small highly jointed fragments, 

 in the upheavals and depressions to which the range has been sub- 

 jected subsequent to their ejection, and by the faulting which has 

 affected them in common with the other rocksj. It is quite possible, 

 also, that these movements may have commenced at a period before 



* Manual of Geology, pp. 712 et seq. 



t The Rev. Mr. Timins's MS. This is the constitution of diabase, or true 

 trap-rock. 



J Professor Phillips takes a similar view respecting the manner in which this 

 brecciated structure has been produced (pp. cit. p. 44). 



