Vol. 50.] ANNIVERSARY ADDRESS OF THE PRESIDENT. 105 



regard as a concession to modern opinion with reference to the 

 origin of many gneissic rocks, not only in the Malverns, but else- 

 where. 



Turning now to the consideration of Dr. Callaway's triple 

 memoir on the Malvern Hills, we find that his first paper offers the 

 results of a preliminary enquiry into the genesis of the crystalline 

 schists. Dr. Callaway expressed his belief that many of the 

 Malvern schists had been formed out of igneous rocks, but he limited 

 his observations, in the present instance, to certain varieties, such 

 as diorite, granite, and felsite. The products of metamorphhm 

 were divided into two groups. Simple scJiists are those derived 

 from the alteration of one kind of rock — thus, hornblende-gneiss 

 from diorite ; mica-gneiss from granite ; and mica-schist from felsite, 

 which latter rock is seen gradually to acquire a parallel structure. 

 Accompanying this mechanical alteration in the felsite is a mineral 

 change ; mica at first appears in very small quantity, either filling 

 cracks or accentuating the parallelism ; in a more advanced stage 

 the mica lies in imperfect folia, and sometimes forms a partial 

 coating to grains of quartz ; finally there is little left but quartz 

 and mica, the latter in folia and enveloping individual quartz- 

 granules. Injection- schists are those formed by the intrusion of 

 veins which had acquired parallelism by pressure ; this group being 

 afterwards subdivided into Schists of primary injection, in which 

 one rock was injected by another, and Schists of secondary injection, 

 formed by the infiltration of secondary minerals along shear-planes. 

 It was further noted that, in the majority of cases, particular 

 varieties of schist occurred in the vicinity of the igneous masses to 

 which they were most nearly related in mineral composition ; and 

 that the mineral banding of rocks in the field was more like vein- 

 structure than stratification. The metamorphism, he states, had 

 been brought about by lateral pressure, evidence of which was to 

 be seen in the intense contortion of granite-veins and in the effects 

 of crushing as observed under the microscope. 



The conclusions to which the Author pointed in this paper were, 

 on the whole, well received ; and it may be said that the belief has 

 continued to gain ground that the Malvern rocks are mainly igneous 

 rocks rendered gneissoid from pressure. There may be a few ex- 

 ceptions, such as the rocks described as quartzite, and certain fine- 

 grained schists not obviously in connexion with igneous masses. 

 It is by no means clear, however, that the views so ingeniously put 

 forward in his two latest papers by Dr. Callaway will meet with 



