Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/416

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The lower Pentowan work lies three quarters of a mile south of the upper, and about half a mile north of the sea. The plain is more contracted here than at the upper work, and the river flows immediately west of the excavation, and nearly on a level with the upper part of it. The excavation measures from north to south about 400 feet, from east to west about 250, and is 54 feet deep. In form it resembles an amphitheatre, being cut into deep stopes (as the miners term them) by which their work is upheld. The miner's object is to come at a deposit of tin five feet thick at the bottom of the pit, and as he works forward he throws behind him the waste matter. Water is conveyed from the river by a wooden trough into an insulated mass of the lower stratum, in which the tin is washed.

The following is the Section of th Strata at the Lower Work.
Depth from
Feet Feet
Stratum 1. Soil with trees growing in great luxuriance, some very old, and gravel towards the bottom 3 3
2. Fine peat. At the bottom are roots of trees, fallen trunks with ivy attached to then, and sticks impregnated with salt. In this stratum also are found sea laver and rushes 12 15
3. Sea mud, which when dry resembles fine grey sand. At the top are masses of leaves compressed flat, whose characters are still to he distinguished. Under the leaves are cockle shells, well preserved. These as the stratum deepens become more decayed. At 4 feet from the bottom of this stratum, and at 31 feet from the surface have been found many bones of animals, viz. the horns of two deer, very large and of equal size; two human skulls, one belonging to a child, the grinders not having yet shot through the jaw; the shoulder and thigh bone of some large animal; and the vertebræ of some smaller animals. At the bottom is a bed of very small shells in great abondance, 1 foot thick, and then a thin layer of small shells in a very delayed state 20 35