CHAP. I.] ABCH^AN TIME. 15 



Dr. Callaway's inquiries into the genesis of the gneissic 

 rocks of the Malvern Hills, and Mr. Peach's experience of 

 the Archaean rocks of Scotland, though not exactly corro- 

 borating Mr. Marr's views, are certainly not at variance 

 with them. Dr. Callaway believes that the hornblende- 

 gneiss of Malvern is a crushed and modified diorite ; 

 that the mica- schists have been similarly formed from 

 f elsite, and the mica-gneiss from granite ; l while he 

 considers some of the banded gneisses were produced by 

 earth-pressures acting upon complex interveining of granite 

 in diorite, resulting in a parallelism of the veins ; so that 

 he would regard many of the Archaean gneisses and schists 

 as metamorphosed igneous rocks, and not as metamorphosed 

 sedimentary rocks. Mr. Peach says : 2 " The gneisses all 

 bear evidence of having been formed by the crushing and re- 

 crystallization of igneous rocks, their schistosity being due 

 to mechanical movement of the particles produced by 

 differential pressure." 



Without entirely acquiescing in Mr. Marr's hypothesis, 

 there can be little doubt that a large portion of the British 

 Archaean rocks are of igneous origin, and that only a small 

 proportion are sedimentary, and that they were accumu- 

 lated in a volcanic district which was eventually elevated 

 into lofty mountain ranges. 



1 " Quart. Journ. Geol. Soc.," vol. xliii. p. 525. 



2 " Proc. Roy. Phys. Soc.," vol. ix. p. 23. 



