Experiments with Modified Mucronate Electrodes.

any matrix f can be expressed as a function of the variables a,, instead of p, q, just as in classical theory we can use (6) as well as (7). The correspondence principle then follows from the asymptotic agreement of classical and quantum canonical transformations. It seems, nevertheless, of interest to have proved the correspondence principle as directly as possible without appeal to iterated transformations. 1 p. A. M. Dirac, Proc. Roy. Soc. London, 113A, 621 (1927). 2 P. Jordan, Zeits. Physik, 40, 809 and 44, 1 (1927). 3 G. Wentzel, Ibid., 38, 518 (1926). 4 L. Brillouin, J. Physique, 7, 353 (1926). 5C. Eckart, Proc. Nat. Acad. Sci., 12, 684 (1926). 6 Born, Heisenberg and Jordan, Zeits. Physik, 35, 563 (1926). 7 Cf., for instance, Muir, Theory of Determinants, vol. II, p. 230. The identity is due originally to Jacobi, Crelle's Journ., 27, 199 (1846), or Gesammelte Werke, iv, 317. 8 H. A. Kramers, Zeits. Physik, 39,828 (1926). P. Jordan, Ibid., 38, 513 (1926); and 41, 797 (1927).