On a theory of electricity and gravitation

This is the second paper by Nordstr{\"o}m on his five dimensional theory. It aims at generalizing the relations $\mathbf{D} = \epsilon \mathbf{E}$, $\mathbf{B} = \mu \mathbf{H}$ of electromagnetism to the five dimensional gravito-electric theory and to show that this is consistent with the principle of equivalence. Some steps are taken toward providing a foundation for a theory of matter. Nordstr{\"o}m hopes, as stated in the conclusion, to show ''that the five dimensional perspective, while still having only a formal content, may however provide footholds for further developments of the theory of gravitation, which otherwise would have been hard to find''.