Collected Papers

This volume in its first part reproduces the treatises and papers wherein Professor H. A. Lorentz developed the electromagnetic theory of phenomena in moving systems up to the point achieved in the relativity theory of uniform translations. We have not included the article in the Encyclopaedie der mathematischen Wissenschaften, Vol. V, number I4, nor the book 'Theory of Electrons', for reasons given previously. The second part of the volume contains the work on the theory ot gravitation. In the early development of the theory the author lays stress on the hypothesis of the stagnant ether, and he so firmly believes in the validity of his formula for the ponderomotive force on electric charges, that he is even prepared to abandon the momentum conservation law (see p. 28). It was Max Abraham who in I903 reconciled Lorentz's formula for the force with the conservation law by interpreting the term at fault as the representation of electromagnetic momentum per unit volume of the field, thus meeting the criticism of Henri Poincare. This interpretation was readily taken over by Lorentz. Again, referring to the transformation formula tor the time variable, Professor Lorentz preferred to think 0/ 'local time' as a mathematical auxiliary. A dmitting and even stressing the impossibility of discrimin­ ating experimentally between local time and absolute time, he never relinquished the belief that the latter words might have a meaning after all.