D O C U M E N T 2 6 0 A U G U S T 1 9 2 8 2 5 9 is the external field in the neighborhood of the singularity. It is also of 1st or- der. is of a higher than first order. Let us write the first of the equations I [by] leaving off terms of higher than second order. We then obtain . Now we imagine that the pole of is “rounded off” then becomes .[15] At the end, we can again go back to the limiting case. We then obtain by integration: and by differentiation, In our further calculations, it is certainly of importance just how behaves at the singularity. If we assume for the time being that we can replace by (the distance of the point considered from the singularity), then we can set out on the right-hand side (if not, there would be additional terms that would give rise to further conditions). The vanishing of outside of the rounding-off region re- quires that the surface integral that is carried out over the area of the rounding-off region  One obtains in which the integral is to be computed over the surface area that encompasses the rounding-off region. would vanish. That then yields the equations of motion For the calculation, we still have to note that the contain only mixed terms of and , and that in , only need be taken into account. Furthermore, in the , one also need consider only the , in the case that the field is due only  a        2 i  t2 ------------- +   = =     *  *  * dV r ------------------- =  x  *  *  x -------------- -dV r ---------------------- =   x  ----------- 1 r -- 1 r 0 ---- 1 r 0 x x  ------------ - *  x  ------------- - 1 r --  1 cosnx 1  2 cosnx 2  3 cosnx 3 + + dS  A r ------ = =    i   a   i   i 44  a   a 44