“If we ignore the mathematics of physics, is there anything that remains? “So asks Prof. Einstein in his introduction to this brilliant little work, which supplies a convincing answer to the question. The introduction states that the book is neither a treatise nor a textbook, and gives no mathematical formulae or experimental details, but treats methodically and philosophically a restricted range of facts to enable the reader to appreciate and understand the limitless perspective and beauty of modern science. Actually the fundamental principles of physics are expounded in the simplest possible language with a wealth of apposite analogies and illustrations, so that the reader feels as if engaged in an absorbing novel. Under the chapter headings of methods of thought in physicsradiation, matter, the nuclei of atoms, matter and radiation, and modern quantum mechanicsall the main features of the picture of modern physics are presented in a co-ordinated and most up-to-date manner. The neutron and positron are treated as integral features in the exposition, and not as matter “received too late for classification”. One is, as it were, taken behind the scenes, and shown with the liberal help of genealogical type diagrams how theories have arisen, the contributions which they made, and how and why their limitations have caused them to be superseded by newer ideas. The more advanced reader will appreciate especially the final chapter in which separate but co-ordinated accounts of the lines of reasoning of de Broglie, Schrodinger, Heisenberg and Dirac are described with a simplicity of style which, under the restriction of excluding mathematics, could scarcely be excelled. The World in Modern Science: Matter and Quanta. By Leopold Infeld. Translated by Louis Infeld. Pp. 287. (London: Victor Gollancz, Ltd., 1934.) 5s. net.