Page:A Book of Dartmoor.djvu/308

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as best she might. They were Quakers, and help was forthcoming from the Friends. William kept his eyes about him, and discovered the china-clay which is found to so large an extent in Devon and Cornwall, and he laid the foundation of the kaolin trade between 1745 and 1750. One of the first places where he identified the clay was on Tregonning Hill in S. Breage parish, Cornwall, and to his dying day he was unaware of the enormous deposits on Lee Moor close to his Plymouth home.

He took out a patent in 1768 for the manufacture of Plymouth china, specimens of which are now eagerly sought after.

Kaolin is dissolved feldspar, deposited from the granite which has yielded to atmospheric and aqueous influences.

The white clay is dug out of pits and then is washed in tanks, in which the clayey sediment is collected. This sediment has, however, first to be purged of much of its mica and coarser particles as the stream in which it is dissolved is conveyed slowly over shallow "launders."

At the bottom of the pits are plugs, and so soon as the settled kaolin is sufficiently thick, these plugs are withdrawn, and the clay, now of the consistency of treacle, is allowed to flow into tanks at a lower level. Here it remains for three weeks or a month to thicken, when it is transferred to the "dry," a long shed with a well-ventilated roof, and with a furnace at one end and flues connected with it that traverse the whole "dry" and discharge into a chimney