The wave equation for a system of N electrons (mass m) and one nucleus (mass M) is set up and solved approximately. If W(m) are the energy levels for M=∞, the energy levels for finite M are (μW(m)m)+∆W, where μ=mM(m+M) and ∆W is calculable. In case N=2 or 3, ∆W is zero except for P levels. For these it is given by Eq. (13), which is derived on the assumption that the wave function is a polynomial of hydrogen functions, each with its own effective nuclear charge. The values of the latter previously determined by one of the authors are used in comparing the calculation with Schüler's experimental data on Li II, λ5485 and Li I, λ6708. The agreement is satisfactory and eliminates one objection to Schüler's interpretation of λ5485.