7 8 D O C . 9 6 A U G U S T 1 9 1 9 Lorentz transformation. It would be different if the radii were considered material, but not the tangential connections of their endpoints.[5] What you say about the measuring rods and clocks placed on the periphery is completely untenable.[6] An unjustifiable transferral of results of the special theory of relativity to accelerated systems (relative to the inertial system) is involved there.[7] Freundlich and Schlick are definitely right here.[8] By your manner of deduction, one could just as well conclude that every light ray must propagate along a straight line relative to an arbitrarily rotating system, etc. Your misunder- standing is very fundamental. I would have much more to say, but face-to-face ar- gument and counterargument are much easier. With best regards, yours, Einstein. 96. From Jean Perrin[1] Paris, 28 August 1919 My dear Einstein, First of all, I would like to tell you that it was a great comfort for everyone here who admired and liked you to learn from our friend Pierre Weiss[2] that since the beginning of the great ordeal and throughout its entire duration you always knew where to look for justice. We shall have a lengthier chat about that someday and, in recollecting our old conversations,[3] I cherish the hope that we should have very closely related con- ceptions of the Ideal towards which Humanity should strive. From the point of view of science, Weiss tells me that you have achieved some very great things, and I am not surprised. I would be very pleased if you could send me (Sorbonne, Paris) a few [offprints]. Without drawing any comparison, toward the end of the war I also managed to write up the lecture I had given in Zurich (Fluorescence, Luminescence), delving somewhat deeper.[4] Above all, I developed an idea that I had already introduced to you (around 1911, I believe, or 1912???) [on] chemical reactions. (You then doubted that any mono- molecular decomposition would take place in gaseous media without a catalyst— but I believe the objection can be removed.) I would be gratified if you read this paper carefully (Matière et Lumière).[5] There you will find, in particular, a theory of radioactivity that, provided it is accurate, would be of importance.[6]