Nordstrom's theory revisited

Maxwell-Nordstrom equations are rederived in the covariant form with respec t to rotations in pseudo-orthogonal (4 + 1)-dimensional space, by the custo mary procedure of contraction of the excitation tensor and of the dual of t he field tensor. For the invariance of these equations under time reversal T, the real fifth coordinate has to be odd with respect to the T-operation. Consequently, a new interpretation of the fifth coordinate is discussed, i n which exp(iwt) is replaced by a function constructed from doubly-periodic Jacobian elliptic functions.