Albert Einstein (1879-1955).

Autograph letter signed ('Papa') to his elder son, Hans Albert, Old Lyme, Connecticut, 16 June 1935.

In German. One page, 278 x 213mm. Provenance: Christie's, 2 December 2004, lot 95.

Constructing 'a general theory of relativity of nuclear processes'. Einstein announces a significant advance in his work: 'What I have discovered is that the centrally symmetrical solutions of neutral mass-points and of electrical masses can be interpreted as singularity-free fields. This allows a possibility of constructing a general theory of relativity of nuclear processes. But the mathematical obstacles to taking it forward are very great'. The letter opens with an expression of pleasure that Hans Albert is finding such 'fertile soil' in his doctoral research (on sediment transport, on which he was to be a leading authority) and Einstein enters into the subject: 'The fact that the individual path of the stone does not depend on the water-speed indicates that the typical repetitive process in water also has the same property (detached vortex areas?)'. It would be good to test this, but 'it is not easy experimentally'. Hans Albert is to let his father know the costs of his doctorate so that he can 'pitch in'. 'I can still remember very well how hard it was for me to steer the feeble financial skiff past this cliff'. He is deeply pessimistic about the advance of Hitlerism ('die Hitlerei') in Europe, and fears a 'great catastrophe', adding brutally of the recently departed British prime minister Ramsay MacDonald 'They have let this muddler MacDonald potter about too long'. In America, there is considerable unemployment amongst academics, so that prospects for Hans Albert are not promising. Nevertheless, Einstein suggests he send his papers to Theodore von Karman at CalTech, adding a further piece of emphatic advice: 'and learn English'. He himself is very much enjoying a small sailing boat which he has hired for the summer, 'the best means to exercise my old bones'.

In spite of his advice to his son, Einstein never became particularly fluent in English during his 20 years' residence in America.

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