110 SELF-INDUCTION OF ELECTRIC CURRENTS IN A THIN ANCHOR-RING [364 incompressible -frictionless fluid round a solid having the form of the ring; for the components of velocity u, v, w are subject to precisely the same conditions as are a, @, 7. If the density be unity, the kinetic energy T of the motion has the expression T=~ x (circulation)2, .........................(46) 07T L having the value given in (44). P.S. March 4.—Sir W. D. Niven, who in 1881 verified some other results for self-induction—those numbered (11), (12) in the paper referred to—has been good enough to confirm the formulae (1), (28) of the present communication, in which I differ from M. Wien.ith that of the magnets or currents in the field, will maintain the normal component of magnetic induction at every point of the sheet unchanged. If at first there is no magnetic action, and no currents in the sheet, then the normal component of magnetic induction will always be zero at every point of the sheet.