3 6 0 D O C . 2 3 1 W A R B U R G A S R E S E A R C H E R Published in Die Naturwissenschaften 10 (1922): 823–828. Date of submission from the cover letter Abs. 281. A draft in Einstein’s hand [1 021] is also available. Major differences between the draft and the published text are noted. [1]For a biographical account, see Wolff 1992. [2]The draft has “von Himmel gefallen” for “vom Zufall gelenkt.” [3]Apparently a four-volume loose-leaf collection of reprints. [4]After “… haben wir nicht,” the draft has the following sentence crossed out: “Benehmen sich die Gasmoleküle wie elastische Kugeln, so würde das dem Reibungskoeffizienten proportionale Produkt Dichte × freie Weglänge weniger rasch abnimmt als die Dichte zunimmt.” [5]On 27 July, the editor, Arnold Berliner, requested that Ilse Einstein check and correct the bibli- ography (Abs. 356). The typed manuscript of the bibliography [1 022] is available.