These brief chapters from a contemplated longer work by the late Lord Snow are uncommonly good, clear expositions of the people and ideas that made the first half of the 20th century the Golden Age of physics. They are also deeply personal. Snow's friend, physicist William Cooper (who edited the last chapters from notes), explains in the introduction that Snow wrote from memory--a surpassingly good memory--of student days and encounters with the eminent, and later of the war and postwar periods. Here then are Rutherford and Bohr, Dirac and Kapitsa, Born and Heisenberg, SchrÃ–dinger and de Broglie, seen as characters and contributors in a historical drama with social, moral, and aesthetic implications. Snow sketches the principal experiments and theories that led to the atom bomb and current particle physics with broad brush strokes, describing each individual's qualities of excellence. Rutherford, for example, had a genius for tackling problems for which he could devise decisive experiments--usually on a shoestring. Snow is harsh on Heisenberg, the committed German nationalist; but for the most part, the characters are multi-dimensional heroes. Snow never lost his faith that science in its curiosity to find out what is ""there"" could ultimately solve technological problems--whether nuclear fusion or feeding the world's poor. He always maintained, moreover, that science had a moral as well as an aesthetic sensibility--as per a 1960 essay appended here. Also present: the famous Einstein-Roosevelt letter about splitting the atom; and a prescient editorial Snow wrote for a September 1939 issue of Discovery, ""A New Means of Destruction?"" The Snow of the ""Two Cultures"" is not in evidence, but the novelist is: the writing combines economy and insight--condensing, but not oversimplifying--to make this last work a remarkable accomplishment, a book that can be profitably and enjoyably read by the earnest student as well as the seasoned sophisticate.