2 5 6 D O C U M E N T 2 6 0 A U G U S T 1 9 2 8 . One then obtains the recursion formula (whose first term is given simply by ). The interesting [aspect] of this is that in this scheme, time enters only quadrati- cally, not (as in the retarded potential) also linearly.[5] This fact is indeed quite wor- thy of being followed up in more detail. But for the rest, we need only the conse- quence that is already a small quantity of first order (when we later set in order to obtain the wave equation), itself is already small in first order, and thus is naturally small in second order. 2) Rearrangement of the equation . The equation can be decomposed as follows:[6] . is small in second order when the differ from only in terms of the quantities of first order. If we write the equation in the form , and take as a strict condition on the coordinates , so that if we introduce the quantities , the system of equations takes on the form[7] I where contains only terms of second order in the  and in derivatives. This is the form of the equations that seems to me to be most suitable for the derivation of the law of motion they are of course still strictly valid.  nn  =  n 2 n 1 – t2 ----------------- - =  0 = 2 t2 -------- -  1 =  2 t2 R ik 0 = R ik 0 = 0    x  ------------ g   x  -----------------------    –  x  -------- g   –     – ... + = = = =   –       + +   g    R ik g ik R – 0 = g  x  ----------- 1 2  g    –  x  ------------------------------- - – 0 =   g    –   1 2 --  g    –   – =     =   x  ---------- - 0 =  