EINSTEIN, ALBERT. Four autograph letters signed ("Papa") to Hans Albert Einstein, Princeton and n.p., 16 April n.y. and n.d. [late 1930s and 1940s]. Together 6¼ pages, 8vo and 4to.
16 April, n.y.: In response to a technical question from Hans Albert, Einstein writes, "concerning the carrying of rocks by water...I have worked out a theoretical formula for you, based on statistical comparison [formula follows]. It is based, however, on the assumption that the stones are moved at irregular intervals of time, but that every movement covers the same distance. If it is usable, it would yield the distance and frequency for different weights of rock and different speeds of the current." He offers to pay the costs for printing Hans Albert's dissertation, and will help with Mileva's problems with the mortgage on her house. "I've been working with great success recently. I like it here [in Princeton]..." Undated: Fatherly advice to Hans Albert on finding a position in the United States. Einstein has spoken to a man at the California Institute of Technology, and will, if necessary, speak to the father of Henry Morgenthau, who knows everyone and will gladly help. Of his own work, Einstein adds, "I go round and round, but don't seem to make much progress." Undated, [c.1940]: Both he and his sister Maja are "in as good condition as possible for old bones," but it would be better for his grandson (Bernhard Einstein) to spend the summer with people his own age. He discusses whether Hans Albert should look for another job, but suggests that even to apply would be unwise in one case, since he is Einstein's son. "There is a vehement campaign of slander against me," and Hans Albert would make himself a target for vengeful people. If Hans Albert intends to patent his invention, his father is willing to look over and improve the application. Undated: Lengthy observations on some calculations in a work Hans Albert has sent him. Einstein cautions that he is not a proper judge, since he is not a specialist and does not know the literature. But a work like this should be "artistic: exact in structure and clear in detail, with nothing unnecessary." His own work is continuing, without great success. He is concerned the Germans may take over Switzerland and has sent a telegram urging Mileva to take refuge in the mountains, perhaps at the home of the Winteler family. He fears that Eduard will be in special danger because the Germans will use him to avenge themselves on Einstein. (4)