Mill-Stones are chiefly composed of quarts and felspar, the latter in small particles, with a little mica ; they are very hard, not susceptible of a polish, and by their numerous unequal angular prominences, are particularly adapted to grinding corn to powder. Mill-stones are principally brought from Normandy in France, and their chemical and mineralogical characters have never vet been sufficiently examined. There is, however, much reason to believe, that if the mountains of Scotland, Ireland or Wales, were minutely investigated, a stone in every respect fit for mills would be found.