Reports and Proceedings — Geological Society of London. 283 



The following communications were read: — 



1. "On Overthrusts at Tintagel (North Cornwall)." ^ By Henry 

 Dewey, F.G.S. 



In this paper the author deals with the geological structure of the 

 Tintagel area. After brief reference to the stratigraphy north of 

 Bodmin Moor, mention is made of the apparent difference in order of 

 superposition of the beds near Tintagel. 



The several types into which the Upper Devonian rocks are divided 

 are next described. The beds in descending order are — 



(6) Tredom Phyllites. 



(5) Trambley Cove Gritty Slates. 



(4) Volcanic Series. 



(3) Barras Nose Beds. 



(2) Woolgarden Phyllites. 



(1) Delabole Slates. 



The above order is preserved for many miles, between the Boscastle 

 coast and Lewannick on the eastern side of Bodmin Moor. A change 

 of strike at Tintagel reveals the anticlinal structure of the district. 

 To the south of the nose of this great fold minor folds ci'oss the strike. 

 These folds increase westwards until they are replaced by overthrusts. 

 Four sections from east to west show the increased folding and over- 

 thrusting towards the northern part of the area. 



The paper concludes with a reference to the age of the folding. 



2. "The Lahat 'Pipe': a Description of a Tin-Ore Deposit in 

 Perak (Federated Malay States)." By John Brooke Scrivener, M.A., 

 F.G.S. (Geologist to the Federated Malay States Government). 



Large quantities of tin-ore have been obtained during recent years 

 in the Kinta district of Perak, principally from detrital deposits, but 

 also in some cases from the limestone which forms the floor of the 

 Kinta Valley. From 1903 till 1907 the Societe des Etains de Kinta 

 secured over 1000 tons of dressed tin-ore from a peculiar deposit which 

 had the form of a pipe in the limestone, measuring only 7 by 

 2 feet at the surface, but widening when followed downwards. It 

 was worked to a depth of 314 feet. The veinstone was a deep red 

 mixture of calcite and iron-oxide, with some quartz, chalybite, and 

 chalcopyrite, but no tourmaline was found in it. In this the cassiterite 

 occurred in irregular pieces and broken fragments, some of which 

 consisted of radiating needles. 



In Kinta the tin-ores occur in the limestone in two different 

 ways — (1) As lodes or veins with fresh sulphides but not iron- 

 oxides. The tin-oxide crystals have a definite arrangement. (2) As 

 transformed masses deposited in fissures. The cassiterite is in 

 rounded grains, and quartz, tourmaline, and other minerals, also well 

 rounded, accompany it. For a long time it has been doubtful to 

 which of these classes the Lahat pipe should be assigned, as it presents 

 some features of each class. Kecently, however, specimens have been 

 obtained showing veins of arsenopyrite and cassiterite in limestone, 

 and from these the author concludes that the Lahat pipe was originally 

 a vein or lode deposit in the limestone, which subsequently afforded 

 a course for surface waters ; these dissolved away the calcite and 



1 Communicated by permission of the Director of H.M. Geological Survey. 



