CORNISH POST-TERTIARY GEOLOGY. 31 



Drift Moor Worlcs near Newhjn. 



Mr. Carne ' says the tin ground in these works rested on the sides 

 and bottom of a clay-lined basin, on all sides except the north, the 

 point at which alluvial deposits resting on mounds of old workings 

 (carried on to a depth of 36 feet) came in. The tin ground was no 

 thicker at the bottom of the basin, 40 feet from the surface, than on 

 its sides, which are so steep as to come within a foot of it. An old 

 rag and chain pump and three copper coins, one Portuguese, with 

 the figures 169 still legible on it, were found in the alluvial debris, 

 the engine being 15 feet from the surface. 



Mr. Carne - mentioned some stream tin works at Douran, noticed 

 by Borlase in 1738. The tin ore was pulverized, and occurred under 

 2 feet of sand and gravel, which becomes 40 feet thick at Douran 

 Hill on the east. 



Treloy, in Parish of St. Columh Minor. 



De la Beche ^ was informed that the tin ground in the Valley of 

 Treloy rests on an unequal surface ; that above the inequality, the 

 tin ground was poor, below it, abundant and mixed with mussel 

 shells, some of which were attached to the rock, as if they had 

 existed prior to the stream-tin formation, at a time when the sea 

 extended up the valley thus far. 



Mr. Henwood * mentioned the occurrence of a thin bed of tin ore 

 at Treloy, covered by 8 to 10 feet of silt, vegetable matter, sand, and 

 mould, and betraying signs of old workings. Celts, coins, rings, 

 brass brooches were found. The rings were supposed to have been 

 magic rings of the Druids ; the coins appeared to be Eoman, a slight 

 crystalline incrustation was noticed on one or two of them. In a 

 later paper ° ]\Ir. Henwood gives the following section of the Treloy 

 works, probably those referred to above : 



1. Successive layers of sand and gravel 8ft. or 1 Oft, 



2. Vegetable remains 2in. to 6m. 



3. Tin ground ..from 6in. to 2ft. 



' Ibid. vol. iv. p. 47. 



2 Ibid. vol. iii. p. 332. 



^ Eeport on Geol. of Corn, and Devon, p. 405. 



* Trans. Eoy. Geol. Soc. Corn. vol. iv. p. 63. 



* Journ. Eoy. Instit. Corn. vol. iv. p. 219. 



