DOCUMENT 58 OCTOBER 1899 237 tive elektrische Kerne sind ohne ponderable Masse, welche die thermischen und elektrischen Erscheinungen in Metallen bedingen" (Doc. 96). Though Einstein was aware of the difficulties in explaining magnetism on this basis, he believed that Drude was "auf dem richtigen Wege" (Doc. 97). Einstein continued to work on his own theory of thermoelectricity for a time, but decided not to publish it (see Doc. 110). A paper by Reinganum[9] that derives the Wiedemann-Franz law from more general assumptions than Drude's convinced Einstein that the fundamental principles of the electron theory were correct (Doc. 111). Nevertheless, Einstein had two specific objections to Drude's version of the theory (see Doc. 115), as he pointed out in a letter to Drude (see Docs. 110, 112). He was gravely disappointed by Drude's reply (see Docs. 114, 115). The nature of Einstein's objections is not known, but a number of criticisms of Drude's theory were published. Reinganum pointed out that the large number of freely moving charge carriers assumed in a metal should give rise to a much higher value of the specific heat than is observed.[10] He also noted that Drude did not take into account the velocity distri- bution of the charge carriers. Drude assumed that currents in metals were carried by charges of both signs, while Thomson's work suggested that such currents were carried exclusively by negative charges.[11] [9] Reinganum 1900 (see Doc. 111, note 6). [10] This problem is mentioned in Einstein 1907, p. 187. [11] See Thomson, J., 1900. Other objections were also raised: Hall discovered a sign error in Drude's calculation of the Thomson effect, corrected in Drude 1902. Drude's derivation of the Wiedemann-Franz law neglected the effect of the electrical field on collision times in calculating the electrical conductivity (see Seeliger 1921, which reviews criticisms of the classical electron theory of metals). 58. To Mileva Maric Mailand. Dienstag [10 October 1899][1] L[iebes] S[üßes?][2] D[oxerl]! Jetzt Sie sind mir eine Schöne! Sitzt schon ganz gemütlich 4 Tage im Examen & hat kein Schnauferlein für ihren braven Herrn Kollegen und Kaffeesaufbrüderchen. Ist das nicht schauderbar? Ich werde mir eine Schauer- predigt einstudieren und sie Ihnen am nächsten Montag persönlich halten, und zwar in aller Frühe. Und wenn das Mädchen sagt, Sie seien ausgegangen & ich sehe Ihre gewichsten Stiefelchen vor der Thüre-wie das so manchmal passieren soll-dann warte ich einfach noch ein bissel oder lasse mich rasieren. ALS (CLE). [1] Dated by the references in this letter and in the preceding one to Einstein's return to Zurich. [2] Underlined twice in the original.