This history is the development of a short story of the Imperial System of Weights and Measures published eleven years ago, but withdrawn when this fuller work took shape. To have made it at all complete would have required a long lifetime of research; to give and discuss every authority, to trace, even to acknowledge, every source of information would have unduly swollen the volume and slackened the interest of the narrative. I offer it with all its shortcomings as an attempt to show the metric instincts of man everywhere and in all time, to trace the origins and evolution of the main national systems, to explain the apparently arbitrary changes which have affected them, to show how the ancient system used by the English-speaking peoples of the world has been able, not only to survive dangerous perturbations in the past, but also to resist the modern revolutionary system which has destroyed so many others less homogeneous, less capable of adaptation to circumstances.

Feb. 1912.