Cambridge: Cambridge University Press, 1922.
First British edition. x, 126 pp. Original purple cloth with gilt spine lettering. Contemporary owner's inscription to front paste down in light pencil, a little dust-soiling to edges, else Fine in Very Good original dust jacket, a few small edge chips with small horizontal tear near head, rub spot to spine panel, slightly dust-soiled. Rare in jacket. Published not long after Bohr's winning the Nobel Prize. Item #140938155