218 Geological Society : — 



In the first instance a separation must be effected of rocks show- 

 ing foliation or lamination, or of which the origin has been sedi- 

 mentary, from those which show no such structure, and which must 

 be regarded as eruptive : there is, in fact, a banded and an un- 

 handed series. The gneisses are altered volcanic tuffs or sedimen- 

 tary rocks of eruptive material derived from the disintegration of 

 rocks of dioritic or syenitic character. 



The rocks of the North Hill, as may be gathered from the tabular 

 classification, are truly eruptive in many cases ; whilst the foliated 

 varieties are made up of the debris of rocks rich in hornblende, 

 which may have had an eruptive origin. The rocks of the Here- 

 fordshire Beacon are chiefly gneissic : the eucrite-basalt occurs at a 

 buttress of the hill. The pegmatite of Swinyard's Hill has appa- 

 rently been faulted into its present position. South of Midsummer 

 Hill fine-grained gneissic rocks, quartzite-schists, &c, are met with. 



There is no reason to suppose that the alteration of any ordinary 

 sedimentary rocks could have resulted in such a vast amount of 

 hornblende as is found in these gneisses. The gneissic rocks of the 

 Malvern Hills may be composed of the detritus of eruptive rocks. 



The rocks of the Malvern Hills show in their structure but little 

 resemblance to the foliation induced by shearing, the crystals seldom 

 exhibiting any marked lenticular form, while there is but little 

 likeness to the pseudo-fluxion structure described by Lehmann, &c. 



The Author concluded that the rocks of the Malvern Hills re- 

 present part of an old district consisting of plutonic and, possibly, 

 of volcanic rocks associated with tuffs, sedimentary rocks com- 

 posed mainly or wholly of eruptive materials, and grits and sand- 

 stones ; that the structural planes in these rocks (sometimes cer- 

 tainly, at others possibly) indicate planes of stratification, and that 

 the foliation, in many cases if not in all, denotes lamination due to 

 deposition either in water or on land surfaces, probably more or 

 less accentuated or altered by the movements which produced the 

 upheavals, subsidences, and flexures prevalent in the range. 



2. " On the alleged Conversion of Crystalline Schists into Igneous 

 Rocks in County Galway." By C. Callaway, Esq., D.Sc, F.G S. 



This paper was an inquiry into the theory, held by many Irish 

 geologists, that granite and other igneous rocks are the last term 

 in a progressive series in the metamorphism of aqueous sediments. 

 The evidence collected by the Author was regarded as entirely 

 hostile to this view. In Knockseefm, the typical section, he found 

 diorite intrusive in gneiss and granite intrusive in the diorite, but 

 no passage between any two. The igneous veins sometimes displayed 

 a foliated structure. At Shaunarea the phenomena were similar ; 

 but the granite in contact with the gneiss was much crushed and 

 decomposed. In the region south of Gleudalough the intrusion of 

 granite in diorite and schist gave rise to the peculiar mixtures which 

 had been described as "metamorphosed conglomerate." The granite 

 was intruded along the joints of the diorite, sometimes separating 

 the joint-blocks from each other, and completely enclosing them. 

 It was noticed that when schists were penetrated by granite isolated 





