On the Theory of the Decrease of Velocity of Moving Electrified Particles on passing through Matter. [Off-print From the Philosophical Magazine (Vol. 25, No. 145) for January 1913 ]. - [THE FOUNDATION OF BOHR'S ATOMIC THEORY - PRESENTATION-COPY]

[London, Taylor & Francis], 1913. 8vo. Original printed wrappers. The fragile wrappers are detached, but fully intact. Merely tiny parts of the thin backstrip lacking. Three small tears to front wrapper, no loss, as well as a couple of creses. Back wrapper with a slight bend to the corner and minor fading to extremities. Pp. (9)-31. Scarce first edition, off-print issue with presentation-inscription, of Bohr's seminal first work on nuclear physics, being the work that lays the foundation for his atomic theory (published before his "On the Constitution of Atoms and Molecules"), in which he is able to conclude "that a hydrogen atom contains only 1 electron outside the positively charged nucleus, and that a helium atom only contains 2 electrons outside the nucleus ." "Bohr's 1913 paper on alpha-particles [i.e. the present], which he had begun in Manchester, and which had led him to the question of atomic structure, marks the transition to his great work, also of 1913, on that same problem. While still in Manchester, he had already begun an early sketch of those entirely new ideas." (Pais, p. 128). The present work must be considered one of the most important to the birth of modern atomic theory.The work is inscribed to renowned Danish physicist and meteorologist Dan la Cour (1876-1942), son of the great Poul la Cour (1846-1908), who is considered the "Danish Edison". The inscription reads as thus: "Hr. Docent Afdelingschef D. la Cour/ med venlig Hilsen/ fra/ Forfatteren." [In Danish, i.e.: "Mr. Assistant Professor Head of Department D. la Cour/ with kind regards/ from/ the author."].Dan la Cour was the assistant of Niels Bohr's father, Christian Bohr, and a well known scientist. From 1903, he was head of the department of the Meteorological Institute, and from 1923 leader thereof. From 1908 he was Associate Professor at the Polytechnic College. His original scientific works are highly respected, as are his original apparati for measuring earth magnetism which are considered highly valuable. "His original intelligence, which in many ways resemble that of his father, also bore fruit in his patenting of various inventions: the "Pyknoprobe", developed to quickly determine the different layers of the sea" a use of termite in quickly heating food and drinks out in the open under unfavourable weather conditions." (From the Danish Encyclopaedia - own translation). He wrote a number of important and esteemed works and was member of the Danish Scientific Academy as well as many prominent international scientific commissions of meteorology and geophysics (i.e. president of the International Geodetical and Geophysical Union). He was also honorary Doctor at the George Washington University. After finishing his studies in Copenhagen, Bohr went to Cambridge in order to pursue his studies on electron theory under the guidance of J.J. Thompson. Thompson, who was beginning to lose interest in the subject by now, did, however, not recognize the genious of the young Bohr, and as soon as he could, Bohr went to Manchester, where Ernest Rutherford had established a laboratory. "There, from March to July 1912, working with utmost concentration, he [i.e. Bohr] laid the foundation for his greatest achievements in physics, the theory of the atomic constitution." (DSB). Bohr's survey of the implications of Rutherford's atomic model had led him to attack the much harder problem which lay at the core of it, namely determining the exact nature of the relation between the atomic number and the number of electrons in the atom. "Bohr obtained a much deeper insight into the problem by a brilliant piece of work, which he - working, as he said, "day and night" - completed with astonishing speed" (DSB), that paper being the present "On the Theory of the Decrease of Velocity of Moving electrified Particles on passing through Matter", which thus constitutes his very first publication on the subject, published immediately after this dense period of 1912, in the Philosop.…