Vol.. 6, 1920 INTERNATIONAL ASTRONOMICAL UNION 
381 
2. That they should aim to observe a large number of stars in duplicate 
in order that data may be forthcoming for the determination of systematic 
differences and systematic errors. 
3. That a catalogue of stellar distances in brief form be published in 
the near future. 
4. Most important of all, that steps be taken at once to determine 
stellar distances by both trigonometric and spectroscopic methods in the 
southern hemisphere. In no respect is our knowledge of southern stars 
as meagre as in this. 
Finally, it is recommended that the International Astronomical Union 
appoint a committee to promote cooperation along the lines indicated. 
Frank Schi^esinger, Chairman, W. S. Adams, S. A. MitcheIvL. 
REPORT OF THE COMMITTEE ON STELI.AR PHOTOMETRY 
The following observations and suggestions are submitted for the con- 
sideration of the American delegates to the meeting of the International 
Astronomical Union, with the hope that they may be helpful in the or- 
ganization of an International Committee on Stellar Photometry. It is 
for this purpose that they are presented, rather than as a program for the 
operations of such a committee when once formed. 
The organization of an International Committee on Stellar Photometry, 
which we herewith recommend, requires an immediate specification of the 
functions to be exercised. These we believe may be summarized as 
follows : 
(1) To advise in the matter of notation, nomenclature, definitions, 
conventions, etc., whose universal adoption will simplify and unify the 
publication and use of photometric results. 
(2) To plan and execute investigations requiring the cooperation of 
several observers or institutions. The necessity for cooperation in such 
investigations may arise from geographical considerations, from the magni- 
tude of the undertaking or from the demands for precision which can be 
satisfied only by combining the results obtained with different instruments 
and imder widely different conditions. 
Thus the systematic observation of variable stars requires operations 
in both northern and southern hemispheres and in different longitudes; 
again, such an undertaking as the reduction of the provisional magnitudes 
of the Carte du del to the normal scale, because of the labor involved if 
for no other reason, could not be carried out by any single institution; 
and, finally, the peculiar difficulties and numerous sources of error involved 
in the establishment of reliable standards of brightness raises an impera- 
tive demand for confirmation which can be satisfied only by concerted and 
cooperative effort. 
The nature of the activities included under (1) is sufficiently obvious 
from the above formulation. There can be no question as to the desira- 
