Bohr (Niels) On the Theory of the Decrease of Velocity of Moving Electrified Particles on Passing Through Matter, first edition, presentation copy inscribed by the author on front cover, offprint from the Philosophical Magazine, 6th series, vol.25 no.145, pp.10-31, original printed wrappers, preserved in modern cloth drop-back box with small leather book-label of Haven O'More, 8vo, 1913.

⁂ A fine and rare presentation copy of the foundation of Bohr's atomic theory. Calculating the decrease in velocity of Alpha particles fired at atoms, Bohr here shows that the decrease depends on the electron structure of the atoms (and in particular their number and frequencies) - a theoretical result in agreement with the empirical data about the atoms.