Published online by Cambridge University Press: 05 April 2014
The first International Astronomical Union meeting in Rome, May 1922
Solar Union in Bonn in 1913 Frank Schlesinger had been able to conclude, as a result of the questionnaire  to 28 prominent spectroscopists from the Committee on the Classification of Stellar Spectra, that ‘… the preference for the Draper classification is nearly unanimous, but… the general feeling among investigators is opposed at the present time of any system as a permanent one’ . (The ISU questionnaire of 1911 is discussed in Section 5.10.)
In practice 1913 represents the point when the Harvard system was universally adopted. Nine years later, at the first meeting of the newly formed International Astronomical Union (IAU) in Rome, in May 1922, the earlier temporary acceptance of this system was formally and unanimously approved as permanent. The chairman of the Spectral Classification Committee was then Walter Adams. By this time six volumes of the Henry Draper Catalogue had been published and the classification of nearly a quarter of a million stars had been completed by Annie Cannon six years previously. The adoption of the Harvard system was therefore no longer an issue: the Adams report prescribed that ‘the Draper Classification or “Harvard System” … should be the basis on which any further extensions should be built. Classification on other and different systems should be abandoned permanently’ , although it was conceded that in ‘cases of great uncertainty Secchi's types may be employed’.