lii 



face of the land, and forming wide plains 

 or plateaux. These tiuly " massive erup- 

 tions " have been held by Eichthofen and 

 others to represent the grand fundamental 

 character of volcanism ; ordinary volcanic 

 cones being regarded merely as parasitic 

 excresences on the subterranean lava 

 reservoirs, very much in the relation of 

 minor cinder cones to their parent volcaro." 

 It may be inferred from these observations 

 which are merely the outcome ofspecula- 



tive contemplation, that one may conceive of 

 magma slowly cooling under the immense 

 pressure of superincumbent rock and unex- 

 posed to the atmosphere without the agency 

 of a true typical " intercalated sill." Might 

 not, also, similar crystalline structure to 

 that of dyke root, or sill be produced in a 

 similar way ? It will be interesting to hear 

 further from Messrs. Twelvetrees and 

 Petterd with special reference to these 

 speculative suggestions. 



