D O C U M E N T S 6 6 , 6 7 M A R C H 1 9 2 2 8 3 66. To Erich Marx [Berlin, after 3 March 1922][1] Was written in 1912.[2] I regret, it is far too outdated, impossible to grant permission. I cannot bring myself to allow the m[anuscri]pt to be published in the present form. 67. To Hans Albert and Eduard Einstein [Berlin,] 4 March 1922 Dear boys, From your letter I see that all is well with you, particularly that noble Musica is flourishing. I meanwhile bought a most lovable sailboat with a sail in impeccable condition,[1] so our time together at the so-called castle will be magnificent.[2] We’re going to play music on Katzenstein’s grand piano, which he’s happy to make available to us.[3] We’ll have to drive there for ½ an hour or walk for an hour, though. But that won’t put us off. You’re entirely right about dancing, d[ear] Albert one has to do something for the fairer sex, whom as experience shows one cannot do without.[4] The status of the gyroscope affair is this: the electrolyte liquid, of specific weight 2, proved not to be stable enough, after all, so water had to be resorted to, which consequently leads to an enlargement of the suspended part.[5] My electrical arrangement is working quite satisfactorily.[6] The ice box is making progress. We’re negotiating a contract with the local firm Borsig right now.[7] The patent issue is still entirely obscure but we do in any event have the right of joint use—in case the other patent, which is still not published, should come into serious conflict with ours in any way. It’s amusing that you both have such similar handwritings, hardly distinguishable. I’m so thrilled about every sign of life from you, even if you have nothing particular to say do write short postcards more often. I’m now planning another light experiment. Cathode rays fall onto a small leaf of mica and cause it to glow at the surface. The light comes out in part directly, in part after reflection off the rear surface. The question is