104 W. A. E. Ussher — Post-Tertiary Geology of Cornwall. 



cretaceous deposit." " They occur at an elevation of between 300 

 and 400 feet above the level of the sea, resting upon the slates of 

 the hill, and partly also on a small portion of the granite rock which 

 there occurs ; the granitic rock and slates being traversed by several 

 tin lodes." " This isolated deposit has not hitherto been found to 

 contain organic remains, with the exception of some traces of plants 

 that have the appearance of Fucoids." 



The following sections are given by De la Beche (Eeport, p. 259) ; 

 Hawkins (Trans. Koy. Geol. Soc. Corn., vol. iv. p. 135, etc.) ; Hen- 

 wood (op. cit. vol. v.) ; respectively — on the North-east of the Beacon. 

 Numbers affixed for reference : 



(1) Head of rubble from hill above or Cobb 3ft. Oin. 



Yellow sand 2ft. Oin. 



Brownish sand with numerous planes dipping at 45° (apparently 



bedding) lift. Oin. 



Light- coloured mining clay 2ft. Oin. 



Blue clay 9ft. Oin. 



Yellow sand 4ft. Oin. 



"White sand 4ft. Oin. 



Yellow sand 3ft. Oin. 



Pebbles resting upon an uneven surface of slate — thickness variable. 



(2) Near Trevaunance — 



Yellow Cobb with Killas rubble 



Fire clay 2ft. Oin. 



Clay and sand 3ft. Oin. 



Pine white gritty sand — depth not ascertained. 



(3) Half a mile from the Beacon — 



Surface 383 feet above high water. 



Clay 2ft. Oin. 



Yellow sand, 7 feet below the surface 8ft. Oin. 



The overburden not mentioned would seem to be 5 feet thick. 



The following sections given by Messrs. Kitto and Davies lie 

 toward the North-east of the Beacon (Trans. B. G. Soc. Corn., vol. ix.) : 



(4) Near the outer margin of the deposit — 



Head 



Yellow sand 



Bed sand 



"White sand 



Pebbles in sand not gone through. 



Sections near the above on N.W. and S.W. 



(5) On N.W.— Head 



Clay with a few pebbles 



Sand 



Sandstone 



Sand with pebbles not gone through. 



(6) On S.W. — Very sandy overburden, with numerous quartz pebbles from the 



size of a marble to that of a walnut, beneath which clay only is raised 

 varying from 6 to 12 feet in thickness. 



On the inner margin of the deposit to the west of the above, 

 "mining operations in 1865 exposed a cliff facing North, 16 feet in 

 height, and 15 feet below the surface," nearly perpendicular, 

 " smoothed and polished " and worn " into caves and hollows." An 

 adit cut through to the sand on the other side proved this to have 

 been in all probability a projection from a main cliff face, which old 



5ft. 



Oin. 



2ft. 



Oin. 



2ft. 



Oin. 



4ft. 



Oin. 



6ft. 



Oin. 



3ft. 



Oin. 



12ft. 



Oin. 



2ft. 



Oin. 



