The Physicists: A Generation That Changed the World, by C. P. Snow. Boston: Little, Brown & Co. 192 pp.$15.95. In December of 1938 two German scientists named Otto Hahn and Fritz Strassmann, with interpretive help from Lise Meitner, discovered nuclear fission. In September of 1939, when the Manhattan Project was as yet nothing more than a worried glimmer in Albert Einstein's eye, a British scientific journal called Discovery carried an editorial which began:
''Some physicists think that, within a few months, science will have produced for military use an explosive a million times more violent than dynamite. It is no secret; laboratories in the United States, Germany, France and England have been working on it feverishly since the Spring. It may not come off.'' Or then again, the editorialist admitted, it might. He went on to note the importance of two questions: ''Will it come off? How will the world be affected if it does?''
The editor of Discovery, and the author of that vigilant editorial, was C. P. Snow.
In other words, Snow is no newcomer to this subject. He was himself trained as a physicist, later served as a tutor in physics at Cambridge, and published his first writings - scientific papers - on crystallographic investigation of molecular structures. During World War II he recruited scientists for the British crash program on radar, and eventually became parliamentary secretary for the ministry of technology.
Meanwhile he wrote his series of novels about scientific practice and civic responsibility and delivered his influential lecture entitled ''The Two Cultures ,'' with its valuable warning about the widening intellectual gap between scientists and the rest of us.
So the late Lord Snow had professional credentials for understanding the story of nuclear physics and the critical role its practitioners have played in this century, and he was strategically placed to watch that story unfold.
The chief lesson of ''The Physicists,'' a meager and slapdash treatment of an engrossing topic, is that authorial credentials and placement, even a bit of lordly eminence, cannot alone make a book worth opening.
The fault is not entirely Snow's. ''The Physicists,'' though described on its jacket as ''the last work'' of C. P. Snow, is in fact merely a first draft, completed just before his death in July of last year. Snow's friend William Cooper tells us, in an introduction, that Snow intended to rewrite the draft at greater length, and this might have partly (but only partly) corrected its deficiencies.
The book aspires to examine an 80-year span in the history of physics - roughly from Roentgen and Becquerel through Rutherford and Einstein to Feynman and Gell-Mann - that has been more enriched by dramatic personalities and discoveries and more troubled with moral and political implications than any similar span ever in any other branch of science.
In places ''The Physicists'' is gratifyingly informative and lucid, especially on certain points of quantum mechanics, and intermittently it offers keen assessments of character. But overall it is shamefully vague, disorganized, and insubstantial, lacking exactly the sort of precision and wealth of concrete detail that would be expected from a writer with Snow's appreciation for science.
Those failings seem the result, not from Snow's untimely death, but from his self-indulgent method. When Cooper asked him some time ago whether this book wouldn't require extensive research, Snow replied, ''I'm writing it largely from memory.''
And so it reads: as the knowledgeable but casual reminiscences of an old man who knew much physics and many physicists. At its very best, in the crisp sketches of personalities, Rutherford and Heisenberg and Paul Dirac among others , it attains some of the charm of Bertrand Russell's ''Portraits from Memory'' - though Lord Snow is not nearly, as a writer of deft English prose, the peer of Lord Russell. But for a real work of history that does justice to the great events and ideas of modern physics, let alone the moral dilemmas, we will have to keep waiting: ''The Physicists'' is no such book.