THE As fcronaifi GflrirInstitute of the University of Amsterdam hafcJy/niique reputation in the astronomical world ae M centre for research in both stellar physics and\mllar statistics. This is due to the work of its. fir"director, Prof. A. Pannekoek, whose retiJtenWi has just been announced (Nature, Nov. 9, p. dote)\* Noteworthy among his investigations was thatVg-hich first established a wide dispersion in the absolute magnitudes of the hot, B-type stars, and so led to the now generally accepted view of the existence of these stars in highly localized clusters. Equally significant was his work on Saha's theory of thermal ionization and on the theory of stellar line contours. He is one of the three pioneers-McCrea and Unsold being the others-responsible for developing a wholly deductive theory of the model stellar atmosphere, while his more recent spectroscopic work on the brighter Cepheids has already led to interesting developments in spectnephotometric technique.