256 W. A. E. Ussher — Pleistocene Geology of Cornwall. 



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 neighbour- 

 ing 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 10ft. Oin. 



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 6in. to 12in. 



7. Dark silt, apparently mixed with decomposed vegetable 



matter 1ft. Oin. 



8. Eoots of trees in their natural position; oaks with fibres 



traceable for 2 feet deep. " From the manner in which 

 they spread there can be no doubt but that the trees have 

 grown and fallen on the spot where their roots are found." 

 Oyster-shells still remain fastened to some of the larger 

 stones and to the stumps of trees 



9. Tin ground, with rounded pieces of granite, and subangular 



pieces of slate and greenstone. Most of the tin occurs in 

 the lower part, from the size of the finest sand to pebbles 

 lOlbs. in weight ; some rocks richly impregnated with tin 

 weigh 2001bs. and upwards. Thickness (including No. 

 8) from ... ... 3ft. to 10ft. 



B. De la Beche (Eeport, p. 403) says, "These works are now 

 abandoned," others on S. of London Apprentice Inn were carried on 

 in 1837 : " from which it would appear that from the general rise 

 of its bottom, the sea had not entered this valley sufficiently high 

 to permit marine deposits to be there accumulated." This probably 

 refers to Mr. Colenso's section of Wheal Virgin Works (T.R.G.S. 

 Corn. vol. iv. p. 38), a mile from Happy Union, in which no sea 

 sand was found. The tin ground betraying signs of old men's 

 workings lay beneath 32 feet of silt and river gravel, with oak, 

 willow, etc., in considerable quantity, with their roots in situ where 

 soil exists. " How far," says Mr. Colenso, " Pentuan Valley extended 

 seawards is conjectural, but at its present declivity of 45 feet to 

 a mile between St. Austell and Pentuan, it must have continued 

 a mile further than it does now." Mr. Smith [Ibid, p. 400) 

 mentions the rapid descent of the valley from Hensborougb (900 to 

 1000 feet in height), and the continuance of a bed of pebbles all 

 the way. 



C. Section of Lower Pentewan work, quarter of a mile from the 

 beach given by Mr. Smith (op. cit.) — 



1. Soil with growing trees, some very old; gravelly towards 



the bottom 3-3 



2. Fine peat, roots of trees, fallen trunks, sticks, ivy, sea 



laver, rushes, impregnated with salt 12-152 



3. Sea mud, with compressed leaves at the top, cockles at 



31 feet from the surface, bones, human skulls (one of a 

 child) deer horns. At the bottom, a bed of very small 

 shells a foot in thickness 20 - 35 



4. Sea mud, oysters, and cockles 4 - 39 



5. Compressed leaves, vegetable matter, a few rotten shells 6^ - 45| 



6. Vegetable matter, rushes, fallen trees, leaves, roots, moss, 



the wings of Coleopterous insects 1'46| 



