Discovering how atoms work. The first collected edition and first English language publication of three talks originally given in Danish and German between 1913 and 1921 while Bohr was working out his Nobel Prize-winning theory of atomic spectra. This copy from the library of British physicist Leslie Fleetwood Bates (1897-1978), who did his doctoral work under Ernest Rutherford at Cambridge and became a specialist in ferromagnetism.

In 1911, when Bohr completed his doctorate, the two groundbreaking theories in physics were Planck's discovery that energy is released from matter in discrete units called quanta, and Rutherford's model of the atom as a dense nucleus surrounded by electrons and a great deal of empty space. This left unanswered the question of why electrons were stable in their orbits and did not fall into the nucleus as predicted by classical physics.

Bohr's great intellectual leap was to combine the two theories, proposing that electron orbits only changed in discrete movements corresponding to Planck's quanta. An atom that absorbed exactly the right amount of energy 'jumped' to a wider orbit, while one that lost the same amount (radiating it as heat and light) 'fell' in a tighter orbit to the nucleus. This theory successfully explained the structure and characteristics of atoms of different elements and how they were able to combine and separate in chemical reactions, and it led directly to the development of quantum mechanics. Bohr was awarded the Nobel Prize in 1922, the same year that this volume was published.

First collected edition and first English language publication of each essay, first impression; 8vo; diagrams within the text, contemporary ownership signature to the front free endpaper and pencilled notes in the margins throughout, spotting to the endpapers and edges of text block; original burgundy cloth, titles to spine gilt, spine rolled and faded, cloth rubbed and a little spotted with some bumps to the edges of the upper board, very good condition; 126pp.