FIRST EDITION, bound full volume, of Stjepan Mohorovi i 's prediction of the existence of positronium. "Positronium (Ps) is a system consisting of an electron and its anti-particle, a positron, bound together into an exotic atom, specifically an onium. The system is unstable: the two particles annihilate each other to predominantly produce two or three gamma-rays, depending on the relative spin states" (Wikipedia). Stjepan Mohorovi i (1890-1980) was a Croatian physicist, geophysicist and meteorologist. He is "often called "'he father of positonium'" because of this, his most significant work. It was experimentally discovered and confirmed in 1951 by Martin Deutsch and became known as positronium. Mohorovi i in his paper also calculated spectra of positronium and predicted the existence of positronium in stars because of which he suggested the identification of possible spectral lines of positronium in spectra of stars. He was searching for spectra of positronium in the sky, but unsuccessfully. Positronium lines were first identified in lab in 1975 by Canter et al. and in outer space in spectra of Crab Nebula 1984 by J. E. McClintock" (ibid). CONDITION: 4to. (11 x 9 inches; 275 x 225mm). Plates and in-text illustrations throughout. Bearing the armorial bookplate of Wellesley College; no library spine markings. Solidly bound in maroon cloth, gilt-lettered at the spine. Minor minor rubbing at the edge tips. Clean throughout. Very good condition.