"Dear Millikan, I have just received a letter from Rutherford which contains some of Blackett's work which may interest you and Anderson. It is that they have capitulated on the question of positive electrons and agree with Anderson that there are present in large numbers among the tertiary or quartinary (or whatever they are) ionizing particles seen in a Wilson photograph of the effects particles of positive charge and electronic mass. ...I take it that Blackett has collected so many photographs of such tracks as those earlier ones of Anderson that he can no longer resist this devastatingly interesting conclusion. Blackett's photos will come out in P.R.S. (Proceedings of the Royal Society) in March. I have a lecture to deliver."