l x x i i I N T R O D U C T I O N T O V O L U M E 1 3 of studying original scientific papers. Such study, besides having its charm, pro- vides a deeper insight into theories. Einstein recommends especially his papers of the years 1905 and 1917, which may reveal overlooked ideas (Einstein 1923f, Doc. 406). VIII Einstein’s earlier assistance in the process of developing the gyrocompass at Her- mann Anschütz-Kaempfe’s factory in Kiel consisted in finding a solution to the problem of making the inner metal sphere that contains the gyroscopes float freely in an outer sphere. The solution—a magnet ring, or wreath, whose magnetic field keeps the inner sphere afloat—had been applied to the device, but a new problem arose. How should power be supplied to the gyroscopes through the two metal spheres and the liquid separating them? Earlier ideas of employing sliding rings or inductive coupling had been abandoned. A search began for a well-conducting liq- uid with low electrolytic decomposition. In addition, Einstein and Anschütz- Kaempfe searched for an appropriate coating for the inner sphere’s outer wall. This coating had to resist the chemical effect of the liquid, but also had to allow the elec- tric current from the electrodes of the outer sphere to reach the inner sphere’s own electrodes. Their collaboration had become of such a nature that Anschütz now proposed that Einstein be rewarded for his consulting not only with luxurious hos- pitality, but also financially. Reluctantly, Einstein accepted the offer and requested that the money be forwarded to his Swiss family (Docs. 9, 94, 225). He also followed with keen interest how Anschütz’s engineers wrestled with the “geomagnetic” experiment he had proposed in October 1921: whether a rotating heated body induces a magnetic field. Apparently, Einstein wanted to find out in a model experiment whether the rotating hot masses within the Earth give rise to its magnetic field, an idea nowadays called a “geodynamo” (Docs. 9, 94, 225, and 239). A legal case also gave Einstein an opportunity to visit Kiel. In 1918, Anschütz had lost a patent case against the Gesellschaft für Nautische Instrumente. He did not give up, and sued the Gesellschaft again in 1922. Einstein participated, as in the earlier case, as Anschütz’s private expert not only in the first court proceedings, but also during the appeal, which Anschütz won thanks mostly to Einstein’s self- described role as a “bogeyman” (see Docs. 116, 154, 226, and 257). Three expert opinions demonstrate that Einstein neither lost his interest in tech- nical problems, nor did his fame as an expert in the most diverse fields of technol- ogy fade away (see also Illy 2012). He wrote short assessments of an aerial survey