. (Chem. & Physics) The theory, advanced by Thomson (Lord Kelvin) on the basis of investigation by Helmholtz, that the atoms are vortically moving ring-shaped masses (or masses of other forms having a similar internal motion) of a homogeneous, incompressible, frictionless fluid. Various properties of such atoms (
vortex atoms) can be mathematically deduced. This theory is now (1998) obsolete, and has been superseded by quantum mechanics, which provides more accurate and detailed explanations of atomic behavior. [ Webster 1913 Suppl. +PJC ]