Rutherford, Ernest. and James Chadwick. "Scattering of Alpha-Particles by Atomic Nuclei and the Law of Force". Offprint: Philosophical Magazine, November, 1925. Pp 889-913, in the original printed wrappers.
Rutherford, Ernest and James Chadwick. "The Scattering of Alpha-Particles by Helium" . Offprint from the Philosophical Magazine, September, 1927. Pp 605-620, in the original printed wrappers.
Nice copies: $200 [See here for Rutherford bibliography.]