Since the last meeting of the Union China, Yugoslavia and South Africa have adhered to the Union, while no country has withdrawn.

At the Paris meeting in 1935 the following resolutions of Commission 3 were adopted by the Union:

1. 1. Que la liste préliminaire de notations préparée par le Président de la Commission soit, après certaines modifications, imprimée dans les Transactions de l’Union à titre de liste recommandée provisoirement, et que les astronomes intéressés à la question soient invités a adresser au Président de la Commission les changements qu’ils y suggéreraient.

2. 2. Que l’Union donne son approbation à la publication d’un complément mentionnant les changements et additions à la liste des Observatoires et des Astronomes publiée en 1931, sous les auspices de l’Union, par l’Observatoire Royal d’Uccle.

3. 3. Que l’Union consacre, si possible, une somme n’excédant pas cinq cents francs or, à aider la publication de ce complément.

   The provisional list of notations was printed, as an appendix to the report of Commission 3, Trans. I.A.U. 5, 18, 1935. A number of astronomers communicated to the President of the Commission suggestions of changes. On the basis of these suggestions a corrected list of notations was prepared.

   Reprints of this list were circulated to the various observatories and suggestions of changes invited. In response to this a number of suggestions were received.

The agenda for the meeting in Stockholm are:

1. (1) Report on the progress of the FK3 catalogue, and the volume of apparent places of the stars in this catalogue.

2. (2) At the meeting in Paris it was suggested that the value of the Gaussian constant k should be fixed, and the President was asked to consult people known to be interested. As complete agreement appears to have been reached, the following resolution will be moved: “That the value of the Gaussian constant k shall be taken as 0-01720 20989 50000, the unit of time being the mean solar day for 1900·0”

At the Paris congress in 1935, Messrs Dittrich, Brasch and Pogo had proposed that Commission 5 should undertake the publication of classical works of astronomy (such as Ptolemy’s Almagest, the works of Copernicus, etc.) which were untranslated or for other reasons difficult of access. The commission decided to form a sub-commission, consisting of Mr Stroobant and the gentlemen named above, to study this question, especially the means for its realization. Mr Stroobant had announced his desire to take this work in hand personally. Prof. Stroobant, however, having deceased in July 1936, and his health having been deficient during several months in advance, the sub-commission has not been able to continue its work. This is a question that ought to be taken up at the Stockholm meeting.

From April 6,1935 (date of the last report) up to the present date (Feb. 26,1938) the Bureau has distributed 723 telegrams and published 174 circulars (Nos. 535-708).

The Bureau has again been supported by a great many colleagues and institutions.

As heretofore, the leading principle in our work has been as far as possible to procure provisional data for the continuous observation of new objects. The telegraphic service has been used when necessary to safeguard new discoveries, while in all cases possible the circulars have been depended on. Thus, as before, in dubious cases we have, to begin with, sent a telegram to a few correspondents only, asking for control. In cases of rediscovery of periodic comets and in other cases, when there was no risk of losing the object, we have distributed the announcement through the circulars.

A circular letter was sent out to all members of the Commission in December 1937, to which the majority have replied. While work is going on steadily in the Observatories where meridian observations are carried out, comparatively few catalogues have been published since 1935. In view of the very full report made three years ago it is only necessary to draw attention to the progress which has been made in the interval.

La commission vient de perdre l’un de ses membres les plus actifs dans l’élaboration et la construction des instruments. Le Dr F. G. Pease est décédé le 7 février 1938, après une très courte maladie qui l’emporta en quelques jours.

Mme Ed. Chandon suggère que la commission étudie systématiquement, aux divers points de vues des observations astronomiques, l’œil, cet instrument auquel tous les autres aboutissent et aux imperfections duquel ils doivent remédier.

L’œil est un instrument multiple. Ses qualités photométriques et colorimétriques jouent un rôle fondamental dans les observations des étoiles variables. Comme instrument de coïncidences, l’astigmatisme qu’il peut présenter n’intervient pas de la même manière dans les observations des passages, dans les mesures des hauteurs, etc.

Periodicity and new properties of the frequency curve. Bruno Hanisch uses the method of autocorrelation introduced by W. Pollack in geophysics for the discovery of periods in the frequency series of sunspots from 1794 to 1925. Dividing the whole interval into three sections he finds an eleven- and an eight-year period common to the three sections, whereas other periods found in the three sections differ widely from each other. The new method gives for the length of the main period II-8 years for the interval 1880 to 1925. This result agrees strikingly with the revolution period of Jupiter (Gerlands Beiträge zur Geophysik, 46, 1935).

La Commission vient de subir une lourde perte en la personne de George Ellery Hale, Directeur honoraire de l’Observatoire du Mont Wilson, décédé le 21 février 1938, à l’âge de 70 ans.

L’enregistrement des phénomènes chromosphériques qui sert de base aux relevés et statistiques publiés régulièrement par divers observatoires, a été poursuivi sans changements notables depuis le dernier congrès. Le tableau reproduit dans Trans. I.A.U. 5, 59, 1935 et dans lequel sont groupés les renseignements relatifs à ces travaux d’observation courante, est donc toujours valable.

The Commission has suffered the heavy loss of Prof. W. Bernheimer, who was co-opted on to our Commission and whose work is well known and appreciated.

The following report touches the subjects of interest to this Commission as treated by the various members and is not an account more or less complete of the work done in them in the three years.

Since the date of the 1935 Paris meeting two total eclipses have been successfully observed. Throughout the long path crossing Siberia and Japan the weather on June 19, 1936 on the whole about lived up to predictions. On account of widely scattered clouds neighbouring expeditions had quite different luck with the weather. In contrast, the June 8, 1937 eclipse was seen throughout the whole track under universally clear skies, which is all the more surprising for the reason that eclipse expeditions to the tropics usually fare badly with the weather. Stewart and Stokley in a ship at sea were able to observe the eclipse with a measured duration of 7 min. 6 sec., the longest period of totality in 1200 years.

The red radiation, 6438.4696 A., emitted by a cadmium lamp of Michelson type was first chosen in 1907 by the International Union for Co-operation in Solar Research (Trans. I.U.S.R. 2, 109, 1907) as a definition of the unit of wave-length. This primary standard was subsequently adopted by the International Astronomical Union (Trans. I.A.U. 1, 35, 1922) and by the International Committee on Weights and Measures (Procès-Verbaux Comité Int. Poids et Mesures (2), 12,67,1927). Specifications for the production of this primary standard were adopted provisionally by the I.A.U. in 1925 (Trans. I.A.U. 2, 47, 232, 1925), and by the I.C.W.M. in 1927 (Procès-Verbaux Comité Int. Poids et Mesures (2), 12, 67, 1927). Three reports of this Commission (Trans. I.A.U. 3, 77, 236, 1928; ibid. 4, 58, 233,1932; ibid. 5, 81, 299, 1935) have discussed the divergences in these specifications and pointed out the unsatisfactory features of each. This discussion culminated in a revised specification (Trans. I.A.U. 5, 303, 1935) which was adopted unanimously by the I.C.W.M. in 1935 (Procès-Verbaux Comité Int. (2), 17, 91,1935).

Depuis le Congrès de 1935, au cours duquel la Commission 15 fut créée, des travaux de plus en plus nombreux ont été effectués sur les sujets rentrant dans le cadre de cette Commission. Quoique aucune grande comète ne soit apparue pendant les trois années 1935-36-37, deux comètes moyennes visibles à l’œil nu: Peltier (1936a) et Finsler (1937f) ont permis des recherches variées auxquelles il faut ajouter celles qu’on a pu faire sur les comètes plus faibles ou moins bien placées: Johnson (1935a), Whipple (1937b), Wilk (1937c) et Encke (1937h). Des études théoriques et statistiques et des ouvrages d’ensemble ont complété ces travaux.

Depuis la dernière Assemblée générale, notre commission a eu le regret de perdre deux de ses membres les plus éminents: M. Paul Stroobant, directeur de l’Observatoire Royal de Belgique et M. W. H. Pickering, ancien directeur des succursales de l’Observatoire de Harvard à Arequipa (Pérou) et Mandeville (Jamaïque). Les recherches de M. Paul Stroobant se rapportent pour une grande partie aux planètes, notamment Mercure, Vénus, les petites planètes et Saturne dont il étudia pendant des années les anneaux. Il faisait partie de notre Union comme président de la 5e commission et membre de beaucoup d’autres.

La centralisation au Bureau international de l’Heure des résultats d’observations de l’Opération internationale de 1933 a été très lente, puisque les dernières données attendues ont été reçues vers la fin de 1937.

Le nombre des stations ayant coopéré à l’Opération internationale et ayant transmis leurs observations à l’organisme centralisateur s’élève à soixante et onze. Ainsi qu’il a été expliqué à notre Commission mixte, lors du Congrès de l’Union géodésique et géophysique internationale tenu à Édimbourg en 1936, ces stations ont été réparties en trois groupes:

Le Ier comprenant vingt Observatoires, disposant chacun de plusieurs horloges de première classe (soit à poids sous pression et à température constantes, soit à quartz piézoélectrique);

In consequence of the decision made by the Fifth General Assembly of the I.A.U. I have been entrusted, from January 1936, with the direction of the Central Bureau for the International Service of Latitudes.

I am much indebted to Prof. Kimura, who preceded me as Director and to Prof. Kohlschütter, Director of the Geodetic Institute of Potsdam, for information and advice, which has been of great assistance to me; therefore I desire to acknowledge to them my deep gratitude.

In view of the considerable ground covered by the Commission at its Paris meetings and the fairly complete record of the activities of institutes and observatories, etc. published in the Minutes, it has not been deemed profitable by the president to call for further reports in advance of the Stockholm meeting. At the Paris meeting it was agreed that such reports be printed independently before each meeting of the Union and that reprints of or references to the published reports be sent to the president. It is hoped that all such reports if ready will be made available before the Stockholm meeting so that they may be summarized by the representatives in attendance or by the president and recorded in the Minutes. With reference to the pronouncement at the Paris meeting “that it is eminently desirable that more attention be given to the development of accurate general perturbations and mean elements on the basis of accurate osculating elements”, the president has visited the Planeten-Institut at Frankfurt and the Rechen-Institut at Berlin and has been in correspondence with the Leningrad Institute. From these sources particularly valuable material has been received.

The Commission formed a Sub-Commission on Zodiacal Light, presided over by Prof. Issei Yamamoto. The constitution of a sub-commission on the light of the night sky and kindred phenomena was proposed, but left in abeyance, pending the Stockholm Meeting. Dr Jean Dufay kindly consented to write, at the president’s request, a paper on the present state of the problem of the light of the night sky, which is printed with this Report.