12 CORNISH POST-TERTIARY GEOI^OGY. 



down tlie cliff face. From the height of the cliffs it is very nnlikeh* 

 that these i^ebbles should have been hurled up by storm waves and 

 S25ray from time to time from the beacli below ; and as there is no 

 reason to suppose that they were brought to their present site b}' 

 human agency, I am inclined to regard them as relics of an old 

 gravel deposit, perhaps roughly contemporaneous with the gravels 

 of Crousa Down and Crowan. 



Sands and Clays of St. Agnes. 



St. Agnes Beacon is encircled on three sides by a deposit of sand 

 and clay, generally resting on stream-tin, and covered on the surface 

 by stony clay. This deposit occurs at more than 360 feet above the 

 sea, and rests on slate, except on the east of the Beacon, where an 

 isolated patch rests upon granite. De la Beche ' gives a section of 

 the deposits. Dr. Boase- another. Mr. Hawkins^ gives four sections 

 of pits at 375 feet above spring-tide high- water. Mr. Henwood * 

 gives a section, and quotes four others given by Mr. Thomas at 

 heights of 383, 377, and 418 feet above high-water. The most 

 complete set of observations is given in a paper by Messrs. Kitto and 

 Davies,* accompanied b}^ a map. A year previous to the publication 

 of this paper, Mr. Eobt. Hunt, F.R.S., Keeper of the Mining Records, 

 kindl}^ lent me ten sections of the St. Agnes deposits, beautifully 

 executed by Mr. A. T. Davies ; also a map. In Mr. Davies' paper I 

 find six of these sections given without illustrations. I have reduced 

 the following four sections from Mr. Davies' illustrations. (See 

 Plate.) The details of those marked C and E are not given in Mr. 

 Davies' paj)er ; section F is noticed, and corresponds to H on the 

 map accompanj'ing the paper; while section A corresponds to J on 

 the paper, being taken in the isolated patch on the granite where 

 the clays attain their maximum thickness. 



(Plate, Fig. 1.) Section A, 24 chains distant from the Beacon 



in the direction of W. 18^ S. 



Soil and overburden 9ft. lin. 



Candle clay 19ft. 7iu. 



Pebbles, boulders, and sand, with a seam of sandstone oft. 2iii. 



Upon waterworn granite. 



' Report on Geol. of Com. and Devon, p. 260. 



2 Trans. Roy. Geol. Soc. Corn. vol. iv. p. 296. 



3 Ibid. p. 135, etc. * J/nd. vol. v. 

 6 Ibid. vol. ix. part 3, p. 196, etc. 



