Section 1 of the Report was adopted without discussion save for the correction of a misprint.

The Report of the Sub-Committee on Standard Velocity Stars in Section 2 was discussed in some detail. The President read a letter from Dr Young urging the more systematic and frequent observation of such stars at different observatories. Dr Plaskett also referred to the desirability of the inclusion of more faint stars of early type, particularly of type A, in the recommended list.

Prof. Salet called attention to his investigations indicating the presence in the large Lick Observatory Catalogue of Radial Velocities of slight systematic differences between the values measured for stars near or far from opposition. It is important to learn whether such differences arise from the value of the constant of aberration or from flexure in the instruments employed. Prof. Salet expressed the desire that observers publish not only the mean values of the radial velocities but individual values, giving the dates and hour angles. Dr Beer supported this suggestion.

M. le Président fait connaître que, à la suite du concours financier apporté au B.I.H. par l’Union internationale de Géodésie et Géophysique à partir du 1er janvier 1933, la Commission 31 s’est transformée en une commission mixte, et aux membres appartenant à l’Union astronomique se sont donc ajoutés des membres de l’Union de Géodésie et Géophysique.

M. le Président a examiné les comptes du Bureau international de l’Heure pour les années 1932 à 1934 et a reconnu que les règlements ont été respectés; les revenus ont été en 1932 de 55773.50 fr.; en 1933 la subvention de l’Union astronomique a été de 39487.30 fr. français; et celle de l’Union de Géodésie et Géophysique de 19980.80 fr. français. En 1934 les subventions ont été respectivement de 39424 fr. et de 20000 fr.

The draft report was adopted with one or two minor alterations.

The Commission discussed the points mentioned in section 12 in the report, “desiderata for future work.”

1. 1. Dr Shapley promised to consider the possibility of using the Bruce telescope for the Durchmusterung of the southern areas, going down to magnitude 18.5 approximately.

2. 2. The President asked Dr Jackson’s opinion about the possibility of observing the meridian positions of the standard stars of the southern areas from —30° downward at the Cape observatory.

Dr Jackson’s objection to such work was on account of the faintness of these standard stars. The whole southern sky from — 30° to the south pole will be repeated photographically with the wide angle lens.

A recommendation to the Union concerning the construction of certain tables was accepted.

A discussion was opened on the subject of collaboration in the study of open clusters. An application to the General Assembly was passed for a recommendation as follows: “That the Union call attention to the important problems connected with the open clusters and determinations of proper motions, radial velocities, magnitudes and spectra along the lines already inaugurated at several observatories.”

It was agreed that Dr Mineur should approach the observatories of the Carte du Ciel on the subject of photographing the open clusters for the future determinations of proper motions.

The President first summarized the present position of the work of determining the solar parallax as given in the Report.

In connection with the determination of the positions of the reference stars it was stated that within the next six months or so the reductions of all the series of photographs will be completed and it will then be possible to co-ordinate the results and publish a definitive list of secondary comparison stars. At the same time it has become apparent that there are appreciable errors in the positions based on the meridian observations of some of the primary stars given in Prof. Kopff’s catalogue. By co-ordinating the measures of the several series of path plates it will be possible to derive corrections to the positions of the Kopff stars, which will still keep them on the system adopted by Prof. Kopff, but will improve their homogeneity.

The Commission spent an hour in a general discussion of problems of stellar constitution. The report as printed was unanimously adopted.

In view of the wide range of topics covered by the Commission, it was agreed that it would be desirable to press for the nomination of a new president for the Commission each three years.

Report

In a discussion of stellar “temperatures” (§ 2.1) Prof. Russell referred to the importance of “ excitation temperatures “, as determined from the ratio of numbers of atoms in two states of different energy in the atom. Dr Minnaert pointed out that this was essentially only a “ brightness temperature “ to which Prof. Russell agreed, but added that in this way “brightness temperatures” could be found for those stars for which no measures of angular diameter were available.