Page:Cornwall; Cambridge county geographies.djvu/98

 82 CORNWALL All the early work was in stream tin. The Cornish tin had this disadvantage that it was not pure like the Dartmoor tin, but was so associated with sulphur that after smelting it had to undergo a second process, and that a delicate one. It had to be " roasted," to get rid of the sulphur, for only thus could the tin be made available. Associated with sulphur it is brittle. We may well doubt whether in early times the double process was understood. Moreover, we know that when we have the first notices of tin in the west, it was Dartmoor and not Cornwall which rendered the largest supply. Shaft-mining did not come in before 1450, when the stream tin was exhausted. The use of the adit cannot be traced back beyond the beginning of the seventeenth century. The only way of draining the mines was by rag and chain pumps, each consisting of an endless chain, broadened at intervals by leathern bindings, to fit snugly into a pipe from 12 to 22 ft. long, worked by a windlass at the surface. To drain a mine of great depth a series of these pumps was necessary. When hydraulic draining-engines were first employed is not known, but even so late as the close of the eighteenth century some mines were drained by the rag and chain pump worked by 36 men. Up to the sixteenth century, wooden shovels and picks are known to have been employed, and shovels were merely iron-shod. There is in the British Museum a MS. calendar of Haroldstone in S. Wales, of the early sixteenth century, in which are representations of the works of the months, and in it the labourers in the