ON THE GEOLOGICAL AGE OF CENTEAL AND WEST COENWALL. 



By J, H. COLLINS, F.G.S., Honorary Memier ; and H. F. COLLINS, Associate 

 of the Royal School of Mines. 



SECOND PAPER. 



CONTENTS. 



Introduction. 



Ladock Beds. (DeTonian ?) 



Additional Notes on the Sandstones. 

 The Helford River Conglomerates 

 Suggested reasons for the absence of fossils. 



Fowey Beds. (Upper Silurian ?) 



Opinions of Peach, Pattison, Couch, Murchison, Egerton, 



a,nd others. 

 Discussion of the Fossil Evidence. 

 Davidson on the Age of the Looe Beds. 

 Greater antiquity of the Fov^ey beds. 



Lower Silurians. 



Geological Horizon of the Quartzytes. 

 Discussion of the Fossil Evidence. 

 Comparison with the Stiper-Stones. 

 Non-existence of any great inversion of Strata. 



Ponsanooth Beds. {Pre-Silurian. Cambrian P) 

 Probable Extension to the Western Mines. 

 Comparison with the Longmynd. 



Intrusive Rocks. 



The Mica Traps. 

 Numerous Localities. 

 Physical Description. 

 Spheroidal Structure. 

 Macroscopic Appearance. 

 Microscopic Characters. 

 Chemical Composition. 

 Geological Age. 

 Economic Value, 



