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GREENSTONE. 



249 



218.---Crucible, containing fused portions of the above 



rock. 



219. — Trafpean rock of a hypersthenic character, appa- 

 rently a greenstone altered, together with the slates with 

 which it is associated, by the intrusion of the neighbour- 

 ing granite.— Higher Fenternaclle, near Camelford, Corn- 

 wall. 



220. — Greenstone, schistose trappean rock, composed 



/< 



This is a continuation of 



a line of greenstone extending across Titch Beacon to 

 beyond Davidstow, one of those facts common to the system 

 of rocks of which it forms a part. Calcareous matter is 

 associated with this rock near Grylls, and attempts have 

 been made to burn this variety for lime, for which it is 

 altogether unfit, the trappean matter speedily melting into 

 a glass, and the lime assisting the process ; that very fusible 

 substance, silicate of lime, being soon produced. — Grylls, 



near Camclford, Cornwall. 



(See "Report on Geology of 



Cornwall, &c," pp. 57 and 58.) 



221. — Vesicular trappean rock. — Forms part of a 

 trappean rock that extends west north-westward to David- 

 stow, and east south-eastward to St. Clether. It is asso- 

 ciated with argillaceous slate, and with a line of rocks 



which frequently contain calcareous matter, and even lime- 

 stones. 



The calcarco-trappean series sweeps round the north of 

 Dartmoor, and, after making a southern curve towards Cal- 

 lington, again sweeps round the Brown Willy and Rough 

 Tor granites, which appear to have forced it out by Tin- 

 tagel. This series is occasionally fossiliferous in its course. 

 -St. Clether, Cornwall. 



222. — Fine grained greenstone, partly vesicular. 

 Forms part of one of several elongated trappean masses 



which occur near Endellyon. 



Map 30.) They vary 



in mineral structure, even at short distances, in the same 

 mass. Judging from the phenomena observable on the 



adjacent coast, these masses of trap have been intruded 



TJprEK 

 Gallery. 



Wall-cases 

 6 and 7. 



\ 



w 



