W. A. E. Ussher — Post- Tertiary Geology of Cornwall. 171 



a. In Pornanvon Cove Mr. Carne (op. cit.) noticed 2 boulder beds 

 (in a matrix of calcareous sand, granitic gravel and clay), separated 

 by a mass of solid granite. The westernmost bed being 4 chains 

 long, 10 feet thick, and overlain by 60 feet of granitic debris ; that 

 on the east was found to be 9 chains long, 20 feet in maximum thick- 

 ness, and surmounted by 20 to 50 feet of granitic debris. The 

 boulders vary in size from that of a hazel nut to 3 feet in diameter; 

 no large slate boulders were noticed. The base of the deposit is 

 about the level of very high spring tides. At Forth Just Mr. Carne 

 found boulders at 15 feet above high- water mark. 



b. Mr. Henwood (T. E. Gr.S. Corn. vol. v. p. 13) mentioned the oc- 

 currence of rounded stones of granite, from the size of a nut to 2 or 

 3 feet in diameter, with a few slate pebbles, and with granitic sand 

 filling the interstices, at from 15 to 20 feet above high water, at 

 Porth Just and Pornanvon. He says that an adit at Wheal Besans 

 Lode, Little Bounds Mine, was driven for several fathoms through 

 one of these beds, which was found to be from 60 to 70 feet in 

 thickness. (In this estimate the overlying Head was probably 

 included.— W.U.) 



c. Miss Carne (T. E. G-. S. Corn. vol. vii. p. 371) stated that the 

 adit of a mine south of Kennal Point enters the cliffs under a mass 

 of pebbles and boulders. 



13. Cape Cornwall. 



a. In the south part of Priest Cove I noticed a few pebbles and 

 subangular stones (one of granite), in olive-brown loam, and, occa- 

 sionally, greyish sand, under 50 to 60 feet of Head, which presents 

 a stratiform appearance through unequal distribution of fragments, 

 and different tints. 



b. In a little cove just north of Cape Cornwall I observed the 

 following section (Fig. 2) : — 



1 

 | 

 >Head. 



^^Mi^&^QM&R —Raised beach. 





Fig. 2. — Cape Cornwall on the North side. 

 1 Inch=24 Feet. 



Head, brown loam "with numerous angular stones, containing 

 larger fragments in the lower 5 feet, with pebbles here 

 and there at and near the base 13ft. Oin. 



upon — gravel of pebbles and subangular fragments of slate 

 (altered), quartz, greenstone, a few of flint, and rounded 

 and subangular granite boulders, in coarse brown and black 

 loamy sand 5ft. Oin. 



