FROM THE ISLANDS OFF THE LIZIED. 317 



posed of a granulitic aggregate of quartz and felspar, actinolite, and 

 garnet. 



(2) Porphyritio greenstone (epidiorite) precisely similar to that 

 described from the Clidgas. 



General Conclusions. 



(1) The outer islands consist largely of coarse gneisses. 



(2) The parent rock of these gneisses may have been an eruptive 

 quartz-diorite or tonalite. 



(3) The inner islands consist largely of granulites and granulitic 

 gneiss. 



(4) Associated with the gneisses and granulites are metamor- 

 phosed basic eruptive rocks in which porphyritio crystals of felspar 

 are frequently present. 



(5) The relations of these basic eruptives to the surrounding 

 rocks have been much disturbed by the forces which have deformed 

 the rock-masses in this district. 



(6) The petrographical characters of the rocks themselves have 

 been affected by these deforming forces, and actinolite-schist has 

 been locally developed out of the intrusive greenstone. 



(7) Some of the rocks of the Labham Reefs are intermediate in 

 character between the granulitic rocks of the inner group of islands 

 and the mica-schists of Polpeor. 



(8) The period of dynamic metamorphism, of which the most 

 striking results are seen in the schists of the south-western portion 

 of the Lizard peninsula, was posterior to the formation of the basic 

 dykes. There is no evidence of igneous action in this district since 

 the period of metamorphism. 



Discussion. 



Prof. EoNNET spoke in high terms of the value of the work, done^ 

 as it was, in a region accessible with difficulty, which time did 

 not permit him to explore when working at the rocks of the main- 

 land. The gneissose rocks are such as he would on a priori grounds 

 have expected to find there, and somewhat resemble the gneiss of the 

 Eddystone Rock. He considered that two structures occurred in 

 the Lizard rocks — an older one, to which some would refer the 

 apparent stratification of the rocks of the country, of a date long 

 anterior to Ordovician times ; and a later one, whose exact age is 

 unknown, which seems to have acted with much energy nearly 

 parallel with the coast-line, which very possibly is near a fault. 



The Rev. E. Hill added his testimony to the extreme diligence 

 required to elucidate an area such as that described. 



