408 MR. J. PARKINSON ON THE GEOLOGY OE [Aug. I903, 



34. The Geology of the Tintagel and Davidstow District 

 (Northern Cornwall). By John Parkinson, Esq., F.G.S. 

 (Read March 25th, 1903.) 



[Plate XXV— Map.] 



Contents. 



Page 



Introduction 408 



Part I {a) Description of the District 408 



(b) Macroscopical Description of the Rocks 411 



Part II. Description of Microscopical Detail 413 



Conclusions 427 



Introduction. 



Since the publication in 1839 of the far-famed Memoir by 

 Sir Henry de la Beche on the ' Geology of Cornwall, Devon & 

 West Somerset,' * a large part of the first-named county has been 

 left comparatively unmolested, alike by the hammer and by the 

 theories of the geologist. Thus the district which lies to the west- 

 ward of the fossiliferous Upper Devonian Beds of South Petherwin 

 and Landlake, from St. Clether, in a westerly direction, via Davidstow 

 and the North Cornwall branch of the London & South- Western 

 Bailway to the coast, has been almost untouched, except for four 

 papers, since the date above mentioned. These are 



S. R. Pattison. ' On Auriferous Quartz-rock in North Cornwall ' Quart. 



Journ. Geol. Soc. vol. x (1854) p. 247. 

 H. B. Holl. Quart. Journ. Geol. Soc. vol. xxiv (1868) pp. 418-19. 

 J. A. Phillips. 'On the so-called "Greenstones" of Central & Eastern 



Cornwall' Quart. Journ. Geol. Soc. vol. xxxiv (1878) p. 471. 

 W. Maynard Hutchings. Geol. Mag. dec. iii, vol. vi (1889) pp. 53, 101, 



&214. 



My sincere thanks are due to Prof. T. G. Bonney, F.E.S., for 

 kind suggestions in the course of the preparation of this paper ; 

 to Lieut.-Gen. C. A. MacMahon, F.R.S., for the loan of slides of 

 the Cock's Tor rock ; to Miss Raisin, D.Sc, for specimens and 

 slides from the Ardennes ; to Mr. G. T. Prior and Dr. J. S. Flett, 

 for invaluable aid in determining some of the minerals ; and to 

 Mr. E. T. Newton, F.R.S., for kind help with the fossils. These 

 are, from the coast east of Tintagel Head (between Barras Gug and 

 Smith's Cliff) forms comparable with Atryjpa flabellata and with 

 Posidonomya ; and Spiinfera Verneuilii 2 from Lanterdan Quarry. 



A list of fossils from Tintagel was given by Holl. 



Part I. — (a) Description of the District. 

 In regard to the general structure of the country, two points are of 



1 Pp. 56-59, 108. 



2 Recorded also by S. R. Pattison from the neighbourhood of Trevivian 

 Farm, Quart. Journ. Geol. Soc. vol. x (1854) p. 247. 



