438 PREHISTORIC EUROPE. 



in the general succession of the heds. At the bottom occurs 

 the "tin-ground," a somewhat tumultuous or torrential accumu- 

 lation of angular and sub-angular stones and rocks mixed with 

 sand and gravel. The blocks, as already mentioned, vary in 

 size from a foot or less up to masses several feet, or even 

 yards, in diameter. The general character of the deposits above 

 the tin- ground will be best gathered from the sections which 

 follow. 



Section of Happy Union Works, Pentuan (1829). 1 



1. Bough river-sand and gravel, here and there mixed 



with sea-sand and silt. A row of wooden piles 

 with their tops 24 feet from the surface, apparently- 

 intended for a bridge, was found on a level with 

 spring- tide low- water . . . . . 20 ft. 



2. Sand ; trees all through it, chiefly oaks, lying in 



all directions ; animal remains, bones of red deer, 



hog, human skulls (?), bones of whale . . 20 ft. 



3. Silt or clay and layers of stones, a conglomerate of 



sand, silt, bones, and wood . . . . 2 ft. 



4. Sand with marine shells ; water draining through 



this bed is salt above, fresh below ... 4 in. 



5. Sludge or silt, brownish to a lead colour in places, 



with recent shells which, particularly the bivalves, 

 are often in layers, double and closed, with the 

 siphonal end upward, rendering it likely that 

 they lived and died there. They are of the same 

 species as those existing in the neighbouring sea. 

 Wood, hazel-nuts, and occasionally bones and 

 horns of deer and oxen, are found in this bed ; a 

 piece of oak shaped as if by man, with a barnacle 

 attached, was found at 2 feet from the top . 10 ft. 



6. A layer of leaves, hazel-nuts, sticks, and moss (in 



a perfect state, almost retaining its natural colour, 

 apparently where it grew). It extends, with some 

 interruptions, across the valley, occurs at 30 feet 

 below low-water mark, and about 48 feet below 

 spring-tide high-water . . . . . 6 in. to 12 in! 



7. Dark silt, apparently mixed with decomposed vege- 



table matter . . . . . . . 1 ft. 



1 De La Beche, Report on the Geology of Cornivall, Devon, and West Somerset, 

 p. 401. The section is given in descending order. 



