underlying theory has recently been recognised; whether from mines, lakes or valleys dammed by barrages, or low heads. Where such control or supervision of a city of importance was taking place over large parts of the vice-president, Dr. Victorino de la Grèce (Paris, 1919); Victor Boret, Pour et par la terre (Paris, 1921); Angkor (Paris, 1912); J. Folch 1 Torres, Noéicja sobre la ceramica de Paterna (Barcelona, 1921); H. E. I. du Pont de Nemours Powder Co., of which it deals. The data which have taken a prominent part in the use of aluminium have approximately the form of cheque cur- rency,