this energy approaches zero. In other words, quasi-particle states can be defined that have an asymptotically precise meaning as one approaches the Fermi surface But the idea was so simple and so fuzzy that I am not sure whether anything was u s au w typically willing to trust his intuition far beyond where logic would take him and in this case, it really paid off. I do recall, however, publishing some rather fu ideas with the same general philosophy, on the subject of itinerant-electron mag nons, in a 1951 paper with Kittel 3. SURFACE PHYSICS I have already mentioned Bardeen' s thesis, in which he showed that an important term in the work function comes from the dipole layer formed at the surface by th departure of the charge distribution in and near the surface cells from the sym metrical form that it has in the interior cells, and in which he showed the importance of exchange and correlation effects for the calculation of this dipole moment.Since the dipole moment must depend on conditions at the surface, and in particular must be different for different crystallographic faces of the same metal, it became clear that previous theories(of which there were many) that had tried to express the work function of a metal as a property of its bulk lattice could never be very accurate. In his Harvard period, Bardeen made a start at estimating the differences between the dipole moments of different crystal faces. A much more systematic attack on this question was carried out by Smoluchowski just before World WarII I was very interested in this work, as my contacts with experimentalists of Nottinghams group at M I.T. had got me interested in thermionic emission, and this interest continued and strengthened in my 1940-1 year at Princeton, where M.H. Nichols of Wayne B. Nottingham's group was now doing postdoctoral work Smoluchowski's work was done, I believe, just as I was moving from my subsequent year at Missouri to New York to do war work. I now remember corresponding with him about it. But several years of hectic involvement with antisubmarine warfare had put all this so completely out of my head that when the after the war I again arted thinking about thermionic emission problems at Bell Laboratories, I read Smoluchowski's paper through to the end with great interest, before discovering in the acknowledgments that i had read it before yen interest in thermionic emission got me involved, in the immediate pre-war in the theory of thermoelectric effects and the thermodynamics of irreversible phenomena. I used some rather fuzzy theories from the Dutch school to derive some correct results about contact potentials between conductors at different temperatures and about the cooling effect accompanying thermionic emission. Some years later it became clear that such results could be derived much more clearly and rigorously on the basis of linear-response theory and the Onsager relations But though Onsager's work had been done some years earlier, its application to many practical problems, such as these, lagged, and even the logic of its derivation