On the Decrease of Velocity of Swiftly Moving Electrified Particles in Passing Through Matter. Offprint from Philosophical Magazine, vol. 30, October 1915

First edition, rare author's presentation offprint. "On the Decrease of Velocity of Swiftly Moving Electrified Particles in Passing Through Matter" is the continuation of Bohr's important work on the behavior of alpha particles passing through a material medium. In an earlier 1913 paper ("On the Theory of the Decrease of Velocity of Moving Electrified Particles on Passing Through Matter") Bohr studied the energy loss of alpha particles through ionization and was able to "express the rate of energy loss in terms of the velocity by a much more accurate formula than had so far been achieved - a formula, in fact, to which modern quantum mechanics adds only nonessential refinements" (DSB). In this 1915 follow-up paper, Bohr "includes the influence of effects due to relativity and to straggling (that is, the fluctuations in energy and in range of individual particles)" (Pais, Niels Bohr's Times, p. 128). 8vo, pp. 581-612. Original printed wrappers (dust-soiled at edges, upper outer corner of front wrapper broken off and reinstated, glue residue at spine).…