This volume of "The Collected Papers of Albert Einstein" presents Einstein's writings for the two-year period starting in October 1909. The initial date marks Einstein's departure from the Swiss Patent Office at Bern, which had been his professional home for seven years, and the beginning of his first academic appointment, at the University of Zurich. The volume concludes with the masterful report that Einstein, by then a full professor at the German-language university in Prague, gave to the original Solvay Congress, the first international meeting devoted to the problems of radiation and the quantum theory. Most of Einstein's efforts during these years went into his struggle with these ever more perplexing problems of quanta, on which he made discouragingly little progress.

Einstein's new academic career naturally required him to teach, and almost half of this volume consists of the previously unpublished notes he wrote in preparation for his lectures on mechanics, on electricity and magnetism, and on kinetic theory and statistical mechanics. The last of these is particularly interesting in reflecting some of his research interests.

Several papers here are concerned with aspects of the special theory of relativity, but it is Einstein's article of June 1911 that is a harbinger of things to come: it contains his calculation of the bending of light in a gravitational field on the basis of his equivalence principle.

Martin J. Klein is Bass Professor of the History of Science and Professor of Physics at Yale University and Senior Editor of The Collected Papers of Albert Einstein. A. J. Kox teaches history of science at the University of Amsterdam, Jurgen Renn is Assistant Professor of Philosophy and Physics at Boston University, and Robert Schulmann is Assistant Professor of History at Boston University."

This volume, the first in the series to be devoted to Einstein's correspondence, begins in June 1902, when he went to work at the Swiss Patent Office. It closes in March 1914, as Einstein left Switzerland to take up his appointment as a member of the Prussian Academy of Sciences in Berlin. The great majority of the more than 500 letters from and to Einstein presented here have not been published before, and some of them will be new even to most Einstein scholars. They give us a much richer picture of Einstein in his twenties and early thirties than we have ever had. We see him through his correspondence with his mother, his wife Mileva, and, from 1912 on, his cousin Elsa, who would later become his second wife. He maintains close ties with old friends, but his circle widens, particularly after 1906, to include a number of his contemporaries in physics such as Max Laue and Paul Ehrenfest. He also develops important relationships with older theorists--Max Planck, Arnold Sommerfeld, and especially H. A. Lorentz.

The letters in this volume clarify the development of his academic career once he leaves the Patent Office in 1909, and bring out the important parts played by such staunch supporters of Einstein as Alfred Kleiner, Fritz Haber, and, above all, Walther Nernst.

Most significant, however, is the way the letters document crucial aspects of Einstein's scientific activity: his concentration for years on the unfathomable problems of quanta and radiation, his extensive knowledge of experimental physics, his many fruitful interactions with experimentalists, and finally his long struggle to generalize the 1905 theory of relativity to include gravitation and accelerated frames of reference.

Presented in this volume are Albert Einstein's writings from his arrival in Berlin in the spring of 1914 to take up his new position at the Prussian Academy of Sciences through the end of 1917. During these years he completed the general theory of relativity--the relativistic theory of gravitation--and this was surely the high point of his scientific life. His writings on relativity in this volume range from general treatments of the theory to detailed calculations of specific consequences and his first attempt at a relativistic account of cosmology. They also include his popular exposition of the special and general theories, first published in 1917 and still a valuable account for the general reader.

As soon as the difficulties on the path to general relativity had been overcome, Einstein returned to the riddles of the quantum theory. His major clarification of the quantum theory of radiation appears here along with his lesser known contribution to the formulation of quantum conditions. This volume also contains the papers describing Einstein's only experimental investigation, a study of Ampere's molecular currents, which he carried out with the Dutch physicist W. J. de Haas.

Before the beginning of World War I, Einstein had never expressed his views on nonscientific subjects. Yet one of his first reactions to this previously unthinkable general war was to sign an "Appeal to Europeans" urging an immediate end to hostilities.

Every document in "The Collected Papers of Albert Einstein" appears in the language in which it was written."

This volume presents Einstein's writings from the final period of his work in Switzerland. Most of the material in Volume 4 documents Einstein's search for a relativistic theory of gravitation, a search that ended in Berlin in the fall of 1915 with the completion of the general theory of relativity.

Three scientific manuscripts, printed here for the first time, provide insights into Einstein's efforts to generalize his original relativity theory into a theory of gravitation. The first is a review article on the special theory of relativity. The second consists of notes that document Einstein's research on gravitation. The third manuscript contains calculations on the problem of the motion of the perihelion of Mercury. The explanation of the observed anomaly of this motion was to become one of the classical tests of general relativity. The existence of such a manuscript has not been known before now. All three of these manuscripts, along with other material in this volume, add significantly to our understanding of the creation of general relativity.