The chief difference to be observed in the strata of the two Pentowan Stream Works, is the want of marine matter in those of the upper. In the lower Stream Work I have described the killas rock, upon which are deposited 5 feet of tin ground, 10 feet of vegetable matter, 24 feet of sea mud, and 3 feet of soil, on a level with which flows the river 54 feet above the solid rock.
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The following notice and sections have also been transmitted to the Society.
British antiquities (celts, spear's heads, &c.) have been discovered in the Stream Works at the depth of 20, 30, and 40 feet, from whence it appears probable that the greatest part of the accumulation of soil has taken place at a comparatively modern period.
An accurate representation and description of the Stream Work at Porth in the parish of St. Blazey, of this county, have been presented to the public by Philip Rashleigh, Esq. in the second part of his Description of British Minerals, published in the year 1802.
| Section of the Pentowan Stram Work in 1807. | |||
| Strata | Feet | Inc. | |
| No 1. | Micaceous sandy clay, interspersed with stones and gravel | 9 | ─ |
| 2. | Peat, intermixed with roots and leaves | 7 | ─ |
| 3. | Sand, in which are found branches and trunks of trees | 8 | ─ |
| 4. | Finer sand with shells, in which bones, horns, &c. are found. | 12 | ─ |
N. B. The horns are chiefly those of cattle and stags; a joint of the vertebra of a whale, and a human skull were likewise found in this stratum, the former is now in the possession of the Rev. John Rogers, of Mawnan, in this county. | |||
| 5. | Coarse gravel | 2 | ─ |
| 6. | Closer sand mixed with clay, with decayed leaves, almost forming peat towards the bottom | 12 | ─ |
| 7. | Loose stones and gravel | 1 | ─ |
| 8. | Tin Ground. | 1 | ─ |
