VOLCANIC ROCKS OF DAETMOOR. 



293 



cated the possible alteration of the boundary lines between the 

 Culm series and the Devonian rocks. 



Eig. 9. — Diagram to illustrate the possible Relation of the Brent-Tor 

 Volcanic Series with that of Saltash. 



N. 



Brent Tor. 



Saltash. 



(The dotted lines indicate rocks now removed by denudation.) 

 C. Carboniferous. D. Devonian. G-. G-ranite of Kingston Down. 



Fig. 10 is an attempt to show in a diagrammatic manner the down- 

 throw of the existing portion of the old Brent Tor volcano between 

 the two faults, which were first described by Dr. HoU. That these 



Fig. 10. Diagram to illustrate the Manner in which part of the Brent 

 Tor Volcano has been faulted. 



A. Chief part of the cone. 



B. Part of the cone faulted down. 



C. Fault running N.W. & S.E. 



D. Fault running nearly N. & S. 



faults originated as radiately disposed fissures emanating from the 

 axis of the cone seems highly probable, since similarly situated 

 fissures are common in many modern volcanos. From this diagram 

 it will be seen that by far the greater portion of the cone has been 

 long since removed by denudation. A considerable amount of the 

 downcast part must also have disappeared, leaving only the mere 

 mole-hill from which I have endeavoured to reconstruct the moun- 

 tain which geologists will always associate with the name of Sir 

 Henry De la Beche. 



The flue of the volcano was probably situated somewhere along 

 the line of junction of the two faults. The superior portion was 



