884: T. G. BONNET ON THE SERPENTINE AND 



48. On the Serpentine and associated Rocks of the Lizard Dis- 

 trict. By tho Rev. T. G. Bonne y, M.A., F.G.S., Fellow, Lec- 

 turer in Natural Science, and late Tutor of St. John's College, 

 Cambridge; with Notes on the Chemical Composition of some of 

 the Rocks of the Lizard District, by W. H. Hudleston, Esq., 

 M.A., F.G.S. (Read May 23, 1877.) 



Contents. 



1. Literature of the subject and Introductory matter. 



2. General description of the west Coast. 



3. General description of the east Coast. 



(a) The coast south of Coverack Cove. 

 (6) The Igneous Rocks of* Coverack Cove. 



4. Some inland sections. 



5. Summary of inferences. 



6. Microscopic examination of the Serpentine. 



7. Conclusion. 



8. Analyses of the rocks. 



Literature of the Subject. 



The following papers occur in the ' Transactions of the Royal 

 Geological Society of Cornwall : ' — ■ 



"Ske'ich of the Geology of the Lizard District," by A. Hajendie, 

 i. p. 32. 



" Hints on the Geology of Cornwall," by Sir H. Davy, i. p. 38. 



" On tha Serpentine District of Cornwall," by the Rev. J. Rogers, 

 ii. p. 410. 



" Contributions towards a Knowledge of the Geology of Cornwall," 

 by H. S. Boase, iv. p. 160. 



The subject is also treated in the following works : — ■ 



"On the Physical Structure of the Lizard District," by Professor 

 Sedgwick (Trans. Cambridge Phil. Soc. i. p. 201). 



" Report on the Geology of Cornwall and Devon," by H. T. Do 

 la Beche (published 1839) . 



" On the Serpentinite of the Lizard," by Profs. "W. King and T. 

 H. Rowney (Phil. Mag. ser. 5, vol. i. p. 280). 



In the last of these papers the authors maintain the metamorphic 

 character of the serpentine, but consider it probably an altered 

 pyroxenic rock, like that of Bufaure in tho Passa-Thal. Tho .paper 

 appears to have been mainly written with the view of calling at- 

 tention to imitative organic, especially Foramiuiferal structures. So 

 far as my experience goes, any thing of this kind is very rare. 



The great work of Sir H. De la Beche, and the shorter paper of 

 Professor Sedgwick, are models of careful observation ; and several 

 things mentioned hereafter have been already noticed by them. 

 The former author strongly inclines to the belief that the serpentine 

 is of igneous origin, though he admits some difficulties. The latter 

 is of the same opinion, but suggests that the gabbro, greenstone 

 (including some of what we now should call hornblende schist), and 

 serpentine may be portions of the same igneous mass, which varied 



