'Light quanta are as good as confirmed'

Einstein begins by elucidating a misconception on Besso's part about the correlation of the elements h and ε in Planck's equations (relating to the transfer of energy in quanta). He goes on 'what is essential is that the statistical consideration which leads to Planck's formula has become uniform and thus the most general imaginable, in that nothing more is assumed about the special property of the molecules concerned than the most general quantum idea. Thus emerges the result ... that in each elementary energy transfer between radiation and matter the impulse amount hν/c is transferred to the molecule. It follows that any such elementary process is an entirely directed process. Thus light quanta are as good as confirmed'. On personal matters, Einstein is pleased to hear of further improvements in his estranged wife Mileva's condition, promising not to 'trouble her any more with the divorce', noting wryly that he has fought the 'corresponding battle with my relatives' (about whether he should marry Elsa Einstein): 'I have learnt to withstand tears'. He has renewed plans to visit Holland, and asks Besso to forward his Swiss citizenship certificate, which he will need for the visa.