The most important event of the period elapsed since the last report of this Commission is the completion by R. G. Aitken of the Extension of Burnham’s General Catalogue of Double Stars. A description of this Extension was given in the report of 4 years ago. The Extension is now published and it is of invaluable help to everyone engaged in double star astronomy. We are all greatly indebted to Dr Aitken for the unselfish way in which he has devoted a large part of his time for the benefit of others.

Fourteen members of the committee have failed to respond to correspondence; nearly all of the others have expressed the definite opinion that non-responsive members should be dropped from committee membership when a new list is prepared a few correspondents indicating however, that the policy should be adopted for Commission 27 only if generally adopted for all commissions of the Union.

During the time elapsed since the last general assembly of the I.A.U., many activities have been pursued by the astronomers engaged in research work in the wide fields of problems concerning nebulae and clusters. In fact a number of important discoveries have been made and earlier work has been extended in a way to consolidate earlier views or revise them. The embarras de richesse in this field and the extremely short time available for the compilation of a report make it impossible to present anything else than a few short notes partly written by heart and only intended to express personal views on the question of how the research work on nebulae and clusters might be carried on.

The following report is mainly restricted to work done since the last meeting of the I.A.U., but in a few cases it has been necessary to mention earlier results.

Investigation of stellar spectra has been active during the last four years. Without attempting to make a complete survey, some important researches may be mentioned.

The theory of the intensities and contours of absorption lines has been discussed by Eddington, Milne, Pannekoek, Woolley, H. H. Plaskett, and others, and has proved to be difficult. For example, no quantitative theory has yet been developed for the residuai intensity which remains in even the strongest lines, although the physical causes underlying the formation of residual intensities are rather obvious. Study of solar lines with light which has left the surface at different angles shows that the processes which produce the wings and the centre are probably different. The most promising line of attack on this intricate problem appears to be in studies of the solar spectrum, where different regions of the disc may be separately investigated, rather than of integrated starlight. The highest dispersion available, even in solar work, will be none too great.

The four years that have elapsed since the last meeting of the International Astronomical Union have witnessed steady progress in the determination of radial velocities, principally at the Mt Wilson Observatory, Pasadena, Cal., the Lick Observatory, Mt Hamilton, Cal., the Yerkes Observatory, Williams Bay, Wis., the Dominion Astrophysical Observatory, Victoria, B.C., the Observatory of the University of Michigan, Ann Arbor, Mich., and the Simeis Observatory in Russia. It will be useful, for the members of the Commission, to give a short summary of the radial velocity work completed and in progress since the last meeting.

Sur la proposition du Comité exécutif, l’Assemblée générale du 13 juillet 1928, réunie à Leyde, adopta la résolution suivante:

“Le Comité exécutif espère que d’ici à la fin de la présente convention (31 décembre 1931) la direction du Bureau de l’Heure pourra être exercée par le Directeur de l’Observatoire de Paris, et qu’après cette date l’activité actuelle du Bureau pourra être conservée sans faire appel aux fonds limités de l’Union, peut-être avec la coopération d’observatoires et autres institutions.”

The following recommendations have been made:

1. That a catalogue of the fainter stars with known proper motions or at least a list of the authorities of the proper motion of the fainter stars should be published (Van Maanen).

2. That the parallax observers are requested to publish the basis of selection of the stars of their observing programme.

1. Catalogue of Primary Reference Stars. Two lists of primary reference stars containing, in all, 821 stars were prepared by Prof. Kopff and published in Ast. Nach.224, No. 5375 and 226, No. 5403. These stars were widely observed at the following Observatories: Babelsberg, Cincinnati, Cape, Greenwich, Bergedorf, Heidelberg, La Plata, Leiden, Lick, Padova, Uccie and Washington. The stars were selected to give as uniform a distribution as possible to a distance of I° on either side of the path of Eros according to the preliminary ephemeris of Prof. Gustav Witt (Ast. Nach.224, No. 5375; M.N.R.A.S.85, 997, 1925). The early observations of Eros in the autumn of 1930 indicated that the actual path of Eros deviated considerably from the path indicated by this ephemeris and that the deviation near the time of opposition, when the motion of Eros was almost entirely in declination, would amount in R.A. to about 15 minutes of arc. The primary comparison stars as selected would thus extend on one side of the path, near opposition, to a distance of only 45’. This necessitated either (1) centring the photographic plates on the computed path of Eros, or (2) centring the photographic plates on Eros itself and selecting and observing sufficient additional primary comparison stars to cover the blank strip. It was finally decided to adopt the second alternative and a third list of reference stars, containing eighty-seven stars, was prepared by Prof. Kopff and published in Ast. Nach.240, No. 5756, with a recommendation that sufficient stars of the second list should be re-observed along with the stars of the new list to enable the new observations to be reduced to the system which Prof. Kopff had meanwhile derived from the observations of the two main lists.

This Commission deals with a subject in which there is Uttle scope for organizing activity. The organization of the observations, which provide the data used in research on the constitution of the stars, is assigned to other Commissions. Theoretical investigations are a matter for individual effort, and cannot be organized by a Committee except in special cases where they involve long computations of routine character.

The first point on the agenda dealt with the standard equinox. The Chairman stated that this Committee had to give their opinion about this point as a consequence of a resolution by the General Assembly.

The Committee adopted the resolution, proposed by Dr Schlesinger, to use 1900 as standard equinox for all catalogues which are not catalogues of precision, and afterwards the year 2000.

In the second place, the Committee discussed the question of the abbreviations for the names of the constellations. The Chairman pointed out that there is a demand for 4-letter abbreviations to be used in cases where a maximum saving of space is not necessary. The proposed 4-letter abbreviations, however, are not intended to replace the 3-letter standard abbreviations as adopted in the meeting at Rome in 1922. Dr Schlesinger moved that the 4-letter abbreviations as used in his Catalogue of Bright Stars be adopted with a few exceptions. Dr Russell suggested a few other exceptions and the Committee finally approved of the following five exceptions: Arie, Cane, Dlph, Tria, and Tr Au, which will be used instead of the abbreviations in the Bright Star Catalogue. In all other cases the abbreviations as printed in the Bright Star Catalogue will be used.

1. Miss Vinter Hansen’s proposal that the equation of time be given with the same sign in all almanacs was referred to the directors of the national ephemerides.

2. There was a discussion of the proposal by Dr L. J. Comrie that efforts be made to eliminate duplicate printing in the national ephemerides. It was moved and carried “That the question of duplicate printing be referred to the directors of the principal almanacs, and that they be requested to report at the next meeting of the Union.”

3. The possibility of adopting a uniform system for star positions was also referred to the directors.

M. Bosler in the absence of Prof. Stroobant, presented the President’s report as printed in the reports (pp. 21-23).

A resolution presented by Mr F. de Roy, on behalf of the Belgian National Committee of Astronomy, on the question of filling the gap between the Bibliographie générale of Houzeau and Lancaster (1880) and the Astronomischer Jahresbericht (1899) was endorsed and adopted.

The Commission further expressed a hope that Prof. Stroobant would be enabled to complete and publish his work of bringing the “Vade Mecum” of Houzeau (1882) up to the date of the Astronomischer Jahresbericht.

Sir Frank Dyson submitted the following resolution, which was seconded by Prof. Van Biesbroeck, and carried:

“The Commission recommends that the yearly subsidy of £66, granted since 1928 by the Union to the Central Bureau of Telegrams, be continued.”

The President described some proposals of modifications to the European code which he thought desirable. By using time instead of arc for Right Ascension, and Declination instead of Polar Distance, anybody receiving a telegram would be able to read it directly, without any computations, whereas its security would remain sufficient. This code is, in the main, similar to one which Prof. Förster had suggested many years ago.

After having marked his agreement with Prof. de Sitter, when he stated in his report (p. 27) that at the present moment there do not appear to be any problems in dynamical astronomy requiring combined action and international co-operation, the Chairman briefly reviewed those problems in dynamical astronomy which have been studied in the past four years.

They include methods for the determination of orbits and their adaptation to the use of computing machines; multiple solutions in the problem of the determination of orbits; researches on the final state of dynamical systems with slowly varying parameters (e.g. with varying masses), applications, for instance, to the problem of tides; general dynamical problems of stability and recurrence; lunar theory (problems of convergence, non-uniformity of the rotation of the Earth); problems of perturbations (development of the perturbation function, the Trojan group and other asteroid problems, satellites); the restricted problem of three bodies (numerical investigations and their mathematical foundation, the problems of “sorts” and “groups” [“Klassen”]; analytical investigations on the non-existence of periodic solutions in the range of critical commensurabilities); regularization of the singularities of the problem of three bodies; special cases of the problems of 3 and n bodies; general mathematical theory of the existence of rotating figures of equilibrium; relativity—gravitation—light.

In connection with the plans of the Pulkovo Observatory for removing one of their vertical circles to the southern hemisphere the following recommendation was proposed by Dr Morgan and seconded by Prof. Boss:

“The Commission regards the proposal of the Pulkovo Observatory to establish the Vertical Circle in as nearly equal a southern latitude as possible with great sympathy. We believe this will be of very great value in the improvement of fundamental decimations.”

Dr Lundmark read a report on the programmes for the Lund meridian circle, which programmes include stars of special interest, such as long- and short-period variables, extremely red non-variable stars, B-emission stars, moving clusters, nebulous stars, nuclei of planetary nebulae and of anagalactic objects, etc. The definite programme will contain at least 3000 stars, results for some 400 of which have already been obtained. It is planned to extend the observations to stars in the southern hemisphere as soon as financial conditions will permit the erection of a southern station.

The Commission discussed and adopted the President’s report and passed the following resolution for submission to the General Assembly:

“La Commission souhaite que l’on se mette d’accord pour définir des nombres caractéristiques pouvant représenter les qualités optiques des grands instruments.”

Dr St John explained why it would be necessary to reorganize Section 12. In the Committee there were too many members and too many sections. It was impossible for the President to write to 70 persons! At the request of the general secretary, propositions would be made for a fresh arrangement.

A first scheme was drawn up by Dr St John, Prof. Abetti, Prof. Brunner, Dr d’Azambuja and Dr Minnaert, in a preliminary meeting where they discussed the reorganization problem.

A provisional list of recommendations based upon the Draft Report prepared by Prof. Fowler served as a guide for discussion and action by the committee. The recommendations, together with a digest of the discussion and the action taken, are reported below as a record of the proceedings of Commission 14.

1. It is recommended that two or more observers should investigate the possibility of simplifying the specification for the production of the primary standard by using a source that will give well-defined fringes with retardations greater than 200,000 wave-lengths. No action taken.