In his history of this complex and dangerous element, noted physicist Jeremy Bernstein describes the steps that were taken to transform plutonium from a laboratory novelty into the nuclear weapon that destroyed Nagasaki.

James Clerk Maxwell published the Treatise on Electricity and Magnetism in 1873. At his death, six years later, his theory of the electromagnetic field was neither well understood nor widely accepted. By the mid-1890s, however, it was regarded as one...