‎"SCHMIDT, G.C. - THE DISCOVERY THAT THORIUM IS RADIOACTIVE.‎
‎Ueber die von den Thorverbindungen und einigen andern Substanzen ausgehende Strahlung.‎

‎Berlin, J.A. Barth, 1898. No wrappers. In ""Annalen der Physik"", Neue Folge Band 65, No 5. Pp. 1-240.. (Entire issue offered, No.5). Titlepage to vol. 65. Stamp on titlepage. Schmidt's paper: pp. 141-151, textillustr. A tear to inner lower corners of pp. 24-32. (not affecting Schmidt's paper). Clean and fine.‎

Reference : 43857

‎First printing of Schmidt's full exposition, in which he describes his discovery of the radioactivity of Thorium. Schmidt and Marie Curie independently demonstrated the radioactive quality, but Schmidt's demonstration took place a few months before Curie's. The discovery was announced, but not described in full, in a short message published in ""Verhandl. d. Phys. Gesellsch. zu Berlin, 1898.""Schmidt made his discovery while examining ""many elements and compounds"" in an effeort to determine whether any of the rays that were emitted bore a resemblance to those that Henri becquerel had found emerging from uranium and uranium compounds. He located only one such element, thorium, and immediately conducted absorption, ionization, reflection, refradction, and poklarization studies to determine the characteristics of its rays. Having combined a misinterpretation of Becquerel's with one of his own, Schmidt concluded that thorium rays most resembled Röntgen rays - a conclusion that soon required revisoln in view of the researches of Marie Curie and Ernest Rutherford.""(DSB XII, p. 191.‎