BY W. G. WOOLNOUGH. 807 



more probably the aggregations mark incipient formation of 

 some new mineral, which, if completely developed, would have 

 converted the rock into a knotted schist. 



Summary. 



Sedimentary formations of Upper Ordovician, Silurian, Permo- 

 Carboniferous, andCainozoic ages are certainly represented, and 

 liave all yielded fossils. Devonian and Triassic rocks are pro- 

 bably absent. 



Two well marked unconformities exist: between the Ordovician 

 and Silurian rocks on the one hand, and between these formations 

 and the Permo-Carboniferous on the other. 



Pre-Permo-Carboniferous formations are intruded by a very 

 interesting mass of h3'persthene-bearing granodiorite, which 

 passes peripherally through a granite-porphyry phase into dacite. 

 It is suggested that this represents the top of a laccolitic mass 

 only just exposed by denudation. The grano-diorite is traversed 

 by veins of aplitic and lamprophyric character, probably com- 

 plementary in chemical composition; and contains many, and 

 sometimes very large, xenoliths. 



Tertiary basalts and basalt-tuffs are extensively developed in 

 the eastern portion of the area studied. 



Extremely interesting contact-phenomena exist between the 

 grano-diorite and the Silurian limestones; and calc-silicate rocks 

 composed of wollastonite, garnet, vesuvianite, pyroxene, and 

 "mica are very extensively developed. 



The microscopic structures of the eruptive and metamorphic 

 rocks are described in some detail, and chemical analyses of 

 several types are given. 



Conchisioii. 



In conclusion, I wish to express my gratitude to Professor 

 David, for his ever-ready and sympathetic assistance; to Mr. 

 Dun for help and suggestion; and to many students for help, 

 both in the field and iu the laboratory. I would especially 

 mention Messrs. L. A. Cotton, B.A., B.Sc, W. N. Benson, B.Sc, 



