2 4 4 D O C U M E N T 2 5 0 A U G U S T 1 9 2 8 250. To Chaim Herman Müntz [Scharbeutz,] 7 August 1928 Dear Mr. Müntz, I found your solution of the integration problem to be very interesting it has re- kindled my courage.[1] It would be very helpful of you, if you could calculate the solution of the problem that belongs to[2] I would also like to add a few general remarks: 1) The have vector character with respect to the index , but not with re- spect to a, since this index refers to the local axes. It is similar with the -ly small , which [are] defined by[3] . One can, however, show that the can be considered as tensors with respect to both indices for rotation and Lorentz transformations, resp. Initially, it seems to weigh against this possibility that in such a transformation, the do not trans- form onto themselves, since does indeed not transform as a tensor of 2nd rank, but rather as one of 1st rank (a vector). But one can define the system in such a way that every infinitesimal rotation of the coordinate system[4] is combined with an equal and opposite rotation of the local system. Then the remain invariant, and the transform as tensor components of second order, as can readily be seen. 2) What appears strange to me in your integration method, is that the individual steps have no transformation-invariant significance. It would be very pleasing if you could go so far as to make the whole procedure invariant, i.e., by working only with tensors. Then the meaning of the method would become more apparent. (Nat- urally, fulfilling this wish is not necessarily required.) 3) You have used the equations as the basis for the integration, corresponding to the invariant . It is noticeable in these approximate equations that the conditions for each axis of the n-Bein frames are isolated, so that no relations are present between the axes. 1 2 3 0 = = = 4 j r = h a ha h a a ha + = ha a h a a ha ha ha – 0 = I 2 ggg =