Page:Cornwall; Cambridge county geographies.djvu/96

 80 CORNWALL facture is carried on in a small way, also the construction of mining and other machinery. Shipbuilding occupies about 870 men. Some brick-making is done, but not to any considerable extent. The real employments supplying the vast majority of the people with bread are mining and quarrying, and agriculture and horticulture. 16. Minerals and Mining. The authentic history of tin-mining in Cornwall begins with the year 1156. It is not mentioned in Domesday, and probably the Conqueror was as ignorant that tin was to be found there as were the Romans. In the year above given the tin mines are mentioned in the Pipe Rolls. In 1198 appears a letter from the Warden of the Stannaries to the Justiciar. In 1156 most of the tin was raised on Dartmoor, but the output now began to rise rapidly. In 1201 King John issued a charter to the Stannaries. In 1305 the Cornish Stannaries were in part dissociated from those in Devon. As already stated, in the beds of the valleys running down from the central ridge are deposits of tin, brought there from the lodes degraded by weather and flood in the central spinal ridge. The specific gravity of the tin ore is 6-8, and as the water rolled away from the heights, it deposited the tin that it had brought away with it. "The ores of tin," wrote Pryce in 1776, "are shode and stream... scattered to some distance from the parent lode, and consisting of pebbly and smoothly angular stones of