  In J.D. Jackson's Classical Electrodynamics textbook, the analysis of Dirac's
charge quantization condition in the presence of a magnetic monopole has a
mathematical omission and an all too brief physical argument that might mislead
some students. This paper presents a detailed derivation of Jackson's main
result, explains the significance of the missing term, and highlights the close
connection between Jackson's findings and Dirac's original argument.
