Nuclear Disintegrations Produced by Slow Charged Particles of Slow Mass WITH Processes Involving Charged Mesons
London and New York: Macmillan and Co., Ltd. and The MacMillan Company 1947. First Edition. 890 pages plus indexes and front matter of individual issues, and volume index (xlvi pp) in rear. 8vo. 7 1/2 x 10 inches. Blue buckram binding. Offered is the entire Volume 159 of Nature, A Weekly Journal of Science, Jan. 4, 1947 to Jun 28, 1947. Ex-corporate library (Caterpillar Tractor Co Research Library), with preliminary pages and advertising (but not original issue wrappers) bound in for each issue. Closely trimmed when rebound, not affecting text. Portions of two issues with some dampstaining lower right. Occasional library stamps, pocket removed from front pastedown. Several places where paper was taped to individual pages, with minor paper loss when removed. The two important papers referenced below are in fine condition. Very Good. Cloth. 
Contains two key articles for which C. F. Powell was awarded the Nobel prize in physics in 1950 "for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method."
The first article, "Nuclear Disintegrations Produced by Slow Charged Particles of Slow Mass" is confirmation of the negative pi meson ( ): "In studying photographic plates exposed to the cosmic rays, we have found a number of multiple disintegrations each of which appears to have been produced by the entry of a slow charged particle into a nucleus."(introduction)
The second article, "Processes Involving Charged Mesons" indicates the first existing of the negative pi meson ( )'s decay into -: "In recent investiations with the photographic method, it has been shown that slow charged particles of small pass, present as a component of the cosmic radiation at high altitudes, can enter nuclei and produce disintegrations with the emission of heavy particles. It is convenient to apply the term "Meson" to any particle witha mass intermediate between that of a proton and an electron. In continuing our experiments we have found evidence of mesons which, at the end of their range, produce secondary mesons. We have also observed transmutations in which slow mesons are ejected from disintegrating nuclei..." (from the introduction).
It is important to note that these experiments and discoveries predated linear accelerators, so the technology to create, and detect collisions was far more difficult - often involving balloons high in the atmosphere, and detection sites deep underground looking for naturally occuring events rather than man-made ones.
Ezhela et. al. : Occhialini 1947 (Nobel Prize, p. 93) and Lattes 1947 (Nobel Prize, p. 96). There is a third paper, found in Nature volume 160, p. 453 which is also related.