An Error in Maxwell's “Electricity and Magnetism”

Abstract

IT may be allowed to me to remark that the error mentioned on pp. 172 and 223 of NATURE has its origin really in Helmholtz's renowned paper (“Ueber die Erhaltungder Kraft,” 1847, p. 67), and that it thence found its way into most of the textbooks on electricity. It has sometimes been detected and hinted at; for the first time, I believe, in C. Neumann's paper published in the Ber. d. k. sächs. Ges. d. Wiss, at Leipzig (1871), “Elektrodynamische Untersuchungen mit besonderer Rücksicht auf das Princip der Energie.” There we find (p. 436) the formula—which is identical with the equation of energy given in NATURE, p. 223, if we put—