CEYSTALLINE SCHISTS 0E THE MALVEE1S" HILLS. 533 



an actual passage between the massive and the foliated diorites ; but 

 if the former were diorites, so were the latter, and I submit that 

 there is nothing in the parallelism of the veining inconsistent with 

 the theory of an igneous origin. But the description of the next 

 variety of gneiss will throw additional light upon this question. 



Granite- diorite- gneiss, formed from veins of Granite in Diorite. — 

 This is the most conspicuous gneiss in the Malvern Hills. The 

 gneiss itself and the rocks out of which it is constructed constitute 

 about one half of the entire mass of the range. The diorite is black 

 and of medium grain (No. 1). The production of the banded struc- 

 ture is well seen in the long ridge extending between the Wych and 

 the Wind's Point. At the western qnarry on the south side of the 

 Wych there is a mass of the diorite with granite veins. It appears 

 to pass into the gneiss of which the section chiefly consists, but 

 junctions are obscured by debris. Similar rocks, in which there is 

 the like association of massive and foliated mixtures of the diorite 

 and the granite, are seen at intervals along the crest of the ridge to 

 the south. At the top of the third summit the relations of the 

 rocks are well seen. At one spot the granite is intrusive in the 

 ordinary irregular veins, but it passes rather abruptly on the north 

 into a rock in which the veins strike in a definite direction to the 

 north-west, producing the banded structure of a gneiss. This rock 

 is also well exposed about the Wind's Point. 



The granite-seams in the gneiss vary considerably in thickness.. 

 Sometimes they are continuous for yards, but frequently they are 

 lenticular in section. They often behave like veins in their rapid 

 attenuation and in their branching habit. Their parallelism is by 

 no means uniform, as they sometimes pass obliquely across the inter- 

 banded diorite. Comparing microscopic specimens of this gneiss 

 with slides from the unfoliated vein-structures in the Wych quarry, 

 I do not hesitate to say that it would be impossible to determine 

 which was gneiss and which was vein-structure. Id both cases 

 there is some epidote and chlorite produced in the diorite at the 

 junction of the granite, and for a little distance from it, while the 

 granite is slightly cracked. 



This banded gneiss is, then, a binary mixture of igneous rocks, in 

 which regional pressure has produced a parallelism of the granite- 

 veins. 



4. Geneeal Remaeks. 



As this paper is strictly introductory, the evidence offered is in- 

 complete ; but it will perhaps suffice to prove that some of the 

 Malvern schists are produced out of igneous rocks, and to create a 

 presumption in favour of a similar origin for other varieties. 



In the formation of some of the schists, the chemical and mineral 

 changes have been very great; but into this division of my subject I 

 have barely entered in the present communication. 



Association of the Gneissic Rocks with the Igneous masses. — It is 

 generally true that particular varieties of gneiss and schist occur in 

 the vicinity of the igneous masses to which they are respectively 



