La Commission vient d’être douloureusement éprouvée par la perte de son Président d’honneur, Henri Deslandres, décédé le 15 janvier 1948, dans sa 95me année. Son nom est et demeurera indissolublement lié à l’invention du spectrohéliographe et à la période de découvertes qui a suivi les premières réalisations de cet instrument. La Commission a perdu également le Père Luis Rodés, S.J., décédé le 7 juin 1939, à l’âge de 58 ans, au moment où il venait d’entreprendre la restauration de l’Observatoire de l’Ebre, qu’il dirigeait depuis 1919.

The report is compiled from information supplied by several members, in response to a request for information. Several members replied that they are not now actively concerned with the subjects with which this Commission is dealing. No attempt has been made to review the work done in these subjects in the years since the last General Assembly of 1938.

Daily determinations of the solar constant have been continued by the staff of the Astrophysical Observatory of the Smithsonian Institution at Montezuma (Chile) and at Table Mountain (U.S.). Apparatus and methods are being developed by Abbot and his co-operators for the daily measurement of atmospheric ozone and of its band of absorption, 9–10 μ.

Since the date of the 1938 Stockholm meeting, there has been vast progress from eclipses both on the observational and the theoretical sides. In the interval there have been five total eclipses: 1940, October 1; 1941, September 21; 1944, January 25; 1945, July 9; and 1947, May 20. In spite of the war and of the ever-present enemy of eclipse observers, clouds, valuable observations were secured from each of the five eclipses.

It is becoming increasingly difficult to draw a line of delimitation between the work of Commission 13 (Eclipses) and of Commission 11 (Chromospheric Phenomena) and Commission 12 (Solar Radiation and the Solar Spectrum). Spectacular developments by the use of coronagraphs at the high-altitude stations in France, in Switzerland and in the United States (Harvard Station at 11,532 ft.) and also by the improved motion-picture techniques developed at the McMath-Hulbert and the Mt Wilson Observatories have made it possible for refined observations of prominences and of the corona to be made outside of a total eclipse.

Barrell has given (Proc. Roy. Soc. A, 186, 164, 1946 and Revue de Métrologie Pratique et Légale, 2e série, 7, 33, 1947) a summary of nine directly measured values of the wavelength of the red line of cadmium in terms of the International Metre.

The values originally reported (column 3) are corrected in column 4 to take account of subsequent conclusions regarding the values to be attributed to the ruled standards of length employed and adjustments to uniform conditions of normal air.

Les travaux effectués en physique cométaire depuis le Congrès de l’U.A.I. en 1938, ont apporté une notable contribution à la connaissance de la constitution de ces astres et des phénomènes dont ils sont le siège. Nous allons résumer très brièvement ceux dont nous avons pu avoir connaissance, une partie des publications étrangères ne nous étant pas encore parvenue. Certains répondent directement aux suggestions et recommandations formulées au dernier Congrès.

Depuis sa dernière réunion, la commission a été cruellement éprouvée par la perte de son ancien président, de son président et de deux de ses membres les plus actifs.

Le Révérend Père Théodore Phillips, président de 1925 à 1935, est décédé le 13 Mars 1942, à l’age de 76 ans. Il avait dirigé, pendant 35 ans, la section de Jupiter de la B.A.A. et effectué un nombre considérable d’observations. Il nous laisse une œuvre très étendue sur Jupiter et ses courants atmosphériques, ainsi que des dessins de Mars remarquables par leur beauté et leur précision.

The discussions of observations of occultations have been published annually in the Astronomical Journal. The publication, dealing with the observations in the year 1942, which appeared in A. J. 51, 144–5 (1945), concludes the series of annual discussions made at the Yale Observatory. Beginning with the observations in the year 1943, the British Nautical Almanac Office has assumed the responsibility for the reduction and discussion of occultations of stars by the Moon.

A discussion of the Moon’s motion based upon about 5000 occultations in the eleven years, 1932–42, and about 1000 Washington meridian circle observations in the years 1933–44 was made by D. Brouwer and A. J. Watts, A. J. 52, 169–76 (1947). Both series were reduced to the FK3 system and corrections for limb error were applied, based upon Hayn’s charts. In the case of the occultations the tables by Watts, A. J. 48, 170 (1940), were used for a partial elimination of the systematic limb effect from the lunation solutions. The meridian circle observations were corrected individually.

Les modalités de la publication ont été décidées lors de l’Assemblée Générale de Stockholm en 1938.

Il est rappelé que le nombre des stations ayant participé à l’opération n’est pas moindre que soixante-et-onze. Le rassemblement des renseignements a été très long et a duré jusqu’à la fin de 1937, soit quatre ans après la fin des mesures.

Il avait été décidé de publier à frais répartis par moitié entre l’U.A.I. et l’U.G.G.I. un volume par station donnant des renseignements et des tableaux très complets relatifs aux observations astronomiques, aux réceptions radiotélégraphiques et à la marche des garde-temps utilisés. On devait en outre publier un fascicule introductif et un volume de conclusions.

When, in May 1922 after the First World War, the I.A.U. and the I.G.G.U. met for the first time it was decided that the systematic study of the motion of the pole should be continued. This study had been commenced over 23 years earlier by the International Geodetical Association and had been continued without interruption during the war, thanks to the keenness of the observers and the work of the Swiss and Dutch geodesists and astronomers, who had undertaken to maintain the necessary contacts between the observing stations and the Potsdam Central Office. The Second World War, which broke out barely two decades later, had more serious consequences for this study. The generous and worthy offer of our Swiss colleagues to be intermediaries between the belligerent countries and to help in the exchange of data between the observing stations and the Central Bureau passed unheeded. The Italian Foreign Minister at the time refused to allow the observing books to be transmitted. We had hoped that, when hostilities were over and communications had been re-established, we should be able to obtain, although late, the complete series of observations.

Après le Congrès de l’U.A.I. Stockholm 1938, M. Delporte, Président de la Commission, s’est mis en rapport avec les membres de la dite Commission élus à Stockholm et avec les membres de pays non adhérents à l’Union et dont la cooptation proposée au meeting de Stockholm avait été acquise par vote. Le déclenchement des hostilités en 1939 a rompu les contacts entre les états. La Belgique encore neutre, a pu servir d’intermédiaire entre le Rechen-Institut de Berlin et la France, l’Angleterre et l’Afrique du Sud pour l’acheminement des éphémérides pour 1940 (Kleine Planeten).

The scope of this Report is to cover briefly the progress in the study of meteors and meteorites since the 1938 meeting of Commission 22. The Sub-Commission on the Zodiacal Light has been expanded to include also the Light of the Night Sky and is now presided over by M. Jean Dufay. The ever-increasing scientific interest in the problems of nocturnal radiations and the fascinating difficulties of interpretation promise an exciting future for research in these two observationally related fields. On the other hand, the present intensive interest in the earth’s upper atmosphere and in ionospheric research makes interpretation in any one field of research in Commission 22 even more dependent upon knowledge of results in the other fields. Hence it appears essential that Commission 22 and its sub-commission keep in close rapport and that a considerable overlapping of membership be maintained.

La longue période écoulée depuis la dernière assemblée générale de l’Union Astronomique Internationale aurait dû marquer dans l’entreprise de la Carte du Ciel l’achèvement de l’œuvre décidée par l’ancien Comité Permanent et une reprise des travaux dans des voies nouvelles ouvertes par le développement de la Science. Dans sa réunion de 1938 la Commission avait examiné comment l’œuvre pourrait se continuer. Nous nous étions alors engagés à apporter à la réunion qui aurait dû se tenir en 1941 des projets précis, conformes aux échanges de vues qui avaient alors eu lieu. Les événements qui ont bouleversé le monde nous en ont empêchés. Ils ont imposé à trop d’entre nous de tout autres soucis que le développement désintéressé d’une œuvre scientifique de longue haleine, et ils ont empêché toute liaison suivie entre le président de la Commission et ses collègues. Nous n’avons pu jusqu’à présent recueillir sur le travail accompli dans les divers observatoires que des renseignements trop insuffisants pour rendre justice à tous. Nous nous excusons auprès de nos collègues et nous les prions de considérer le rapport actuel comme un rapport préliminaire que nous espérons compléter avant la réunion de Zürich.

The determination of stellar parallaxes photographically using occulting shutters initiated by Schlesinger at Yerkes in 1903 and taken up vigorously at a number of observatories in the northern hemisphere about 1913 and in the southern hemisphere about 1925 has resulted in the determination of more than 9000 parallaxes relating to more than 5000 stars.

The position at the end of 1947 compared with that at the end of 1934 (as shown in I.A.U. Transactions, Vol. 5, 149) is approximately as follows, although for want of official figures some of the data are only estimates.

Since the last report of our Commission, now 10 years ago, there has been important progress in the development of photometric methods, notably the increase in sensitivity of the photoelectric cell. This improvement opens a wide field of useful work even with smaller instruments in the hands of skilled observers. As the cell can only deal with one object at a time, it is desirable that an increased number of instruments be adapted for this kind of work.

The photographic method, which is now antiquated in every case where the highest accuracy is required, will still maintain itself when the problem is to obtain approximate information about a large number of stars within a reasonable time and for the photometry of the very faintest stars which can be reached.

The effect which the war has had on the progress of Astronomy in general, and of Double Star Astronomy in particular, cannot yet be reliably estimated, but we can already say that it is severe and will be felt for many years to come. Its least serious (because, we may hope, only temporary) aspect is the delay in the publication of observations. This effect may be mitigated if observers will communicate their unpublished results and forward reprints of their publications to the two central offices: Lick Observatory for declinations +90° to −30°, Union Observatory for −19° to −90°. If this be done, information supplied by these offices could include unpublished results.

Nomenclature. Le Comité Exécutif réuni à Copenhague en mars 1946 a pris différentes décisions intéressant la Commission 27 (voir Circulaire VI, 2). La sous-commission chargée de la désignation des étoiles variables a publié les 42e et 43e listes, contenant respectivement 123 et 1051 variables dénommées. Ces listes avaient été préparées par Boris W. Kukarkin et Paul P. Parenago. Les règles adoptées sont énumérées dans l’Introduction de la 43e liste.

The Commission on Extra-Galactic Nebulae held three meetings to discuss informally the principal observational and theoretical problems of the extra-galactic nebulae. One resolution was drafted and adopted pointing out the desirability of having Dr C. O. Lampland’s valuable nebulae photographs published.

The Commission on Stellar Spectra records great progress in its field of investigation. We have reached the stage where a concerted attack can be made on two problems of fundamental importance which consciously or unconsciously have been the principal aim of stellar spectroscopists. The first is the problem of the abundances of the chemical elements in their relation to the question of nuclear transformations and the origin of the elements. The other is the problem of the origin of the stars and of their subsequent evolution.

Since the last meeting of the Union, this Commission has lost two valued members, Dr W. E. Harper and Dr J. S. Plaskett, a past-President of this Commission. Both Harper and Plaskett made extensive contributions in the field of stellar radial velocities.

The recent war seriously hindered research at all observatories, many of the institutions carrying on with reduced staffs and greatly diminished resources. The most serious blow to the work of this Commission was the destruction of the Pulkova and Simeis Observatories. The sympathy of the Commission is extended to our Russian colleagues for the loss of their splendid equipment and the destruction of their accumulated photographs. The hope is expressed that their important spectroscopic researches, so tragically interrupted, may soon be resumed.

La sixième Assemblée Générale de l’Union Astronomique Internationale adopta, d’après la proposition de la Commission de l’Heure, la résolution suivante:

La Commission approuve la proposition britannique transmise par le Comité exécutif de l’U.A.I. d’adopter à partir du 1er janvier 1940 les positions d’étoiles du système FK3 pour les déterminations d’heure et leur utilisation en vue de l’émission des signaux horaires.