The Chinese were early acquainted with the existence of coal, and knew of its industrial value to the extent of using it for the baking of porcelain. The fact of its extensive existence in Great Britain, and the valuable uses to which it might be put, did not, however, meet with much notice until the ninth century, when, owing to the decrease of the forest-area, and consequently of the supply of wood-charcoal therefrom, it began to attract attention as affording an excellent substitute for charcoal. The coal-miner was, however, still a creation of the future, and even as peat is collected in Ireland at the present day for fuel, without the laborious process of mining for it, so those people living in coal-bearing districts found their needs satisfied by the quantity of coal, small as it was, which appeared ready to hand on the sides of the carboniferous mountains. Till then, and for a long time afterwards, the principal source of fuel consisted of vast forests, amidst which the charcoal-burners, or "colliers" as they were even then called, lived out their lonely existence in preparing charcoal and hewing wood, for the fires of the baronial halls and stately castles then swarming throughout the land. As the forests became used up, recourse was had more and more to coal, and in 1239 the first charter dealing with and recognising the importance of the supplies was granted to the freemen of Newcastle, according them permission to dig for coals in the Castle fields. About the same time a coal-pit at Preston, Haddingtonshire, was granted to the monks of Newbattle.