^{page 32 note 1} Glacial Geology of Northumberland, p. 102.Google Scholar

^{page 32 note 2} Geology of Northumberland and Durham, p. 15, and “Certain Surface Features of the Glacial Deposits of the Tyne Valley”: Nat. Hist. Trans. Northumberland, etc., vol. xi, pt. iii, 1893.Google Scholar

^{page 32 note 3} Metric tons throughout.Google Scholar

^{page 33 note 1} The figures for 1803 to 1883 have been estimated from the world's decennial production given in Messrs. Nicol Brown & Turnbull's A Century of Copper. Subsequent figures up to the year 1908 are from the Chief Inspector of Mines' Report, part iv. The figure for the year 1913 is from Merton's Tables, and that for 1918 from the Engineering and Mining Journal.Google Scholar

^{page 35 note 1} The present copper production of the United Kingdom is derived mainly from “precipitate” got by treating water from the old Parys and Mona mines in Anglesey.Google Scholar

^{page 36 note 1} Merton.Google Scholar

^{page 36 note 2} Mineral Industry.Google Scholar

^{page 36 note 3} Home Office.Google Scholar

^{page 36 note 4} By Nicol Brown & Turnbull in A Century of Copper.Google Scholar

^{page 39 note 1} The Mineral Resource of the United States, 1916, p. 642.Google Scholar

^{page 39 note 2} The Strategy of Minerals, New York, 1919, p. 153.Google Scholar