M.: This would lead one to assume that Slade knew more physics than the Leipzig professor. For in a great number of experiments Zöllner himself had prescribed the conditions, including all contrivances which made deception so much the more unlikely, since Slade himself could not know what Zöllner's intentions were. It was a question of Electricity, Magnetism, Optics including prepared conditions of polarization, involved Mechanics, in short, things that Zöllner as a professional physicist understood thoroughly, and which, moreover, were controlled by others of his profession. Among the latter was the celebrated professor of Electricity, Wilhelm Weber, who, like Zöllner, found himself faced by phenomena that were utterly incomprehensible to him. It would be a profitable undertaking to bring these dissertations to light again, and it would easily be recognized that the things described actually deal with scientific problems and have not the remotest connexion with tricks of magic. For example, there is an account of an incredible anatomical feat. On flour which had been placed carefully in a dish beforehand, there suddenly appeared the imprint of a naked human foot, whilst Slade was present at a certain distance, being fully clothed and subject to careful scrutiny. The footprint showed all the surface-details of the skin, as was confirmed by authorities, just as only a left foot could produce them, but not an artificial copy. EINSTEIN: And from this Zöllner inferred the intervention of supernatural beings? He would have done better to measure the dimensions of the foot. M.: So he did--at once. A difference of four centimetres between the length of Slade's foot and the copy was disclosed. This riddle, like so many others, remained unexplained. I must repeat that I am not in the slightest degree disposed to assert that occult phenomena really occur, but am interested only in seeing that they are investigated carefully by qualified persons. EINSTEIN: Your remarks show that Leipzig scientists did so at that time with no better result than that Zöllners mental confusion became still greater. M.: The conjecture remains that the Leipzig experiments, abundant as they were, did not suffice. Allow me to ask a direct question, Professor. Supposing another such agent of miracles should appear, would you yourself feel impelled to test him experimentally? EINSTEIN: Your question is misdirected. I explained above that I share the point of view taken up by Dubois-Reymond and his colleagues.