Mr. Ward on the Granitoid Rocks of the Lake-district. 163 



results to be considered as preliminary only, since the complete in- 

 vestigation would necessarily occupy far more time than was at his 

 disposal ; at the same time he ventured to hope that general accu- 

 racy was insured, while pointing to the many little-known causes 

 which might affect the conclusions. 



Part II. On the Eskdale and Shop Granites, with their associated 

 Metamorphic Modes. 



The author brought forward evidence in this paper to prove the 

 possibility of the formation of granite by the extreme metamorphism 

 of volcanic rocks. The passage is shown in the field, and may be 

 observed in a complete series of hand specimens. Frequently, 

 indeed, the actual junction is well marked ; but in other cases the 

 transition is gradual ; and there occur, at some little distance from 

 the main mass, inlying patches of what may be called bastard 

 granite. The microscopic examination proves the passage from a 

 distinctly fragmentary ash to a distinctly crystalline rock, and to 

 granite itself. Also the chemical composition of the altered rocks 

 agrees very closely with that of the granite. 



Both Eskdale and Shap granite were believed to have been formed 

 mainly from the rocks of the volcanic series by metamorphism at 

 considerable depths ; but the granite of Shap was thought to be in 

 great measure intrusive amongst those particular beds which are now 

 seen around it. A decided increase in the proportion of phosphoric 

 acid was noted in the volcanic rocks on approaching the granite, and 

 a decrease in carbonic acid. 



Part III. On the Skiddaw Granite and its associated Metamorphic 

 rocks. 



The subject was treated under the three heads of (1) Examination 

 in the Field, (2) Microscopical examination, (3)\CJiemical examination ; 

 and the following were the general results arrived at. The meta- 

 morphism of the Skicldaw slate extends for many miles around the 

 several granitic masses, and commences by the formation of small 

 spots which become developed into chiastolite crystals. The chias- 

 tolite slate passes into spotted schist, by the great increase of the 

 small oblong spots arranged along planes of foliation ; and mica ap- 

 pears. The spotted schist graduates into mica-schist, which, however, 

 often retains to the last faint spots, and occasionally chiastolite 

 crystals. The junction between the mica-schist and the granite is 

 generally rather abrupt. On the whole, chemical and field evidence 

 especially are against regarding the granite now exposed as the 

 result of the extreme metamorphism of the Skiddaw slates imme- 

 diately around it ; but whether it may not have resulted from the 

 metamorphism of underlying parts of the same series is an open 

 question. The great contortion of the mica-schist around the gra- 

 nitic centres may be in part due to the at any rate partially in- 

 trusive character of the granite. 



In an Appendix abstracts of papers by various authors who have 

 written in connexion with the subject were given. 



