'The Apparent Existence of Easily Deflectable Positives,' pp. 238-239 in Science, New Series, Vol. 76, No. 1967, 9 September 1932. [With:] 'The Positive Electron,' pp. 491-494 in The Physical Review, Second Series, Vol. 43, No. 6, 15 March 1933. This item is unavailable.'The Apparent Existence of Easily Deflectable Positives,' pp. 238-239 in Science, New Series, Vol. 76, No. 1967, 9 September 1932. [With:] 'The Positive Electron,' pp. 491-494 in The Physical Review, Second Series, Vol. 43, No. 6, 15 March 1933

The Discovery of Antimatter. First edition, journal issues in the original printed wrappers, of the two papers in which the positron - the positively-charged antiparticle of the electron and the first experimental evidence of antimatter - entered the scientific record: the short notice of 9 September 1932 in Science, in which Anderson staked his claim as discoverer, and the definitive paper of 15 March 1933 in The Physical Review, carrying the now-iconic cloud-chamber photograph that compelled a sceptical physics community to assent. The Nobel Prize in Physics 1936 was awarded to Anderson for the discovery of the positron, shared with Victor Hess for the detection of cosmic rays. A positive counterpart to the electron had been implicit in P. A. M. Dirac's relativistic wave equation of 1928, and in 1931 Dirac had explicitly predicted a new kind of particle identical to the electron in mass but opposite in charge, an anti-electron in his own phrase; Anderson, working in near-complete isolation from European theoretical physics, was unaware of Dirac's prediction, and maintained to the end of his life that the discovery had been an entirely accidental one. Anderson's papers belong to that small and captivating class of twentieth-century results in which a decisive experiment walks unwittingly into a theoretical landscape already prepared for it. What is offered here - both landmark journal issues in the original printed wrappers, in the physical state in which Anderson's contemporaries received the news - is decidedly uncommon, the Science note in this state considerably rarer still. Carl David Anderson (1905-1991), born in New York City to Swedish immigrants and raised largely in Los Angeles after his parents' divorce, took both his B.S. (1927) and Ph.D. magna cum laude (1930) at the California Institute of Technology, and remained at Caltech for the whole of his career. His supervisor Robert A. Millikan - Nobel laureate of 1923, measurer of the electron's charge, and the unchallenged sovereign of American physics in the interwar years - had in the late 1920s turned his attention to the penetrating radiation from outer space that Victor Hess had detected in 1912 using balloon-borne electrometers. It was Millikan who in 1925 coined the term cosmic rays, and Millikan who remained convinced - incorrectly, as matters turned out - that these rays were the birth pangs of new elements forming in interstellar space. To test the hypothesis he required precise energy measurements, and at Caltech he established three parallel research programmes, each built around a different detector: electroscopes under Victor Neher, Geiger counters under William Pickering, and cloud chambers in a strong magnetic field under Anderson. The three techniques were complementary: electroscopes gave integrated ionisation rates, Geiger counters registered the arrival of individual particles, and cloud chambers alone rendered visible the particle's actual trajectory, from whose curvature in a magnetic field both the momentum and the sign of charge could be read off. The combination gave Caltech in the early 1930s a concentration of cosmic-ray instrumentation unrivalled anywhere outside the Cavendish. The cloud chamber - C. T. R. Wilson's 1911 invention, for which Wilson shared the 1927 Nobel Prize - was effectively an aquarium for sub-atomic particles: a sealed vessel filled with saturated vapour which, when abruptly expanded by a piston, would condense into droplets along the ionisation trails left by passing charged particles; the tracks could then be photographed. Anderson, designing the apparatus himself, built an unusually powerful instrument of this kind, surrounded by a water-cooled electromagnet capable of producing a field of roughly 1.5 tesla (15,000 gauss) - strong enough to curve visibly the paths of even the most energetic cosmic particles. He installed it atop the Guggenheim Aeronautical Laboratory at Caltech, whose generous electrical supply had be.…