OP THE MALVERN HILLS. 



507 



which in many cases are, I think, either altered tuffs or are com- 

 posed of the debris of eruptive rocks rich in hornblende. The rocks 

 of the Worcestershire Beacon appear to be mainly eruptive. Those 

 of the Herefordshire Beacon are^I believe, chiefly gneissic ; but the 

 exposures are not sufficiently numerous or good to enable me to say 

 much on this point, and the time for more careful examination was 

 wanting. The eucrite, basalt, &c, which I have classed with the 

 general mass of this beacou, occur in a buttress of the hill, which, 

 according to Dr. Holl, consists of " Primordial rocks." 



The northern part of Swinyard's Hill is composed of pegmatitic 

 or granitic rocks of varying coarseness. The altered diabase in the 

 Hollybush quarry forms part of the southern end of Midsummer 

 Hill. A vein of pegmatite, consisting in great part of a red felspar, 

 is, at the present time, exposed in the lower part of the quarry. 

 South of Midsummer Hill we meet with fine-grained gneissic rocks, 

 quartzite-schist, quartzite, and altered sandstones, which form, I 

 believe, the highest and least altered part of this Archaean series. 



The views advanced in the first part of this paper appear there- 

 fore to be, as a rule, borne out by the microscopic examination of 

 the rocks, except that those of a truly eruptive character are much 

 more plentiful than I had at first imagined. 



The Malvern Range may, I think, now be regarded as part of an 

 old land where denudation had laid bare certain plutonic rocks, and 

 where volcanic activity was very great ; for whether we look upon 

 these gneissic rocks as beds of volcanic ejectamenta, or regard them 

 as of sedimentar}- origin, there seems to be little doubt that they 

 are composed of the minerals which constitute eruptive rocks, and 

 there appears to be no reason to assume that the alteration of any 

 ordinary sedimentary rocks, such as slates and sandstones, could have 

 resulted in the development of such a vast amount of hornblende. 

 It may be argued that there is no appreciable difference in much of 

 the hornblende occurring in the foliated rocks from that in the 

 adjacent and non-foliated syenites and diorites, and that it is there- 

 fore probable that the foliation has been induced in truly eruptive 

 rocks by earth-movements*; yet, granting this, how comes it that 

 all of the rocks are not foliated? The pressure or movement which 

 would affect one bed would naturally affect those in its proximity ; 

 yet we meet with great variety in these beds both in texture and 

 in structural characters. The facts do not seem to me to bear out 

 the conclusion that earth-movements, at all events in the Malvern 

 Eange, have begotten foliation, except, perhaps, on a very small 

 scale. We know too little as yet of the rocks which are formed 

 from the waste of districts composed mainly of eruptive materials. 

 Whence come our hornblende-slates and schists, chlorite-schists, 

 mica-schists, schorl-schists, &c, the constituents of which are either 

 those of eruptive rocks or their alteration-products, such as epidote, 



* Such apparently bedded structure, accompanied by differences in texture, 

 is described by Prof. Bonney, in his Presidential Address to this Society ( J 8S6) r 

 by the name pseudostromatism, which he regards as the result of "a crushing. 

 in situ of zones of the original coarse-grained rock." 



