Vol.. 6, 1920 INTERNATIONAL ASTRONOMICAL UNION 377 
4. That in particular a preliminary distribution of the necessary ob- 
servational and computational activities among the countries represented 
in the Union be agreed upon, on the basis of such offers as may be received 
from the different countries. 
5. That the American Delegation pledge that it will arrange for the 
care of the observational and computational work incident to comets and 
asteroids discovered in the United States. 
A. O. Lkuschn^r, Chairman, E. W. Brown, G. H. Pe^te^rs. 
APPENDIX A 
MEMORANDUM ON CIvASSlFlCATlON OF PLANETS 
Class a. — Asteroids for which accurate definitive orbits and general 
perturbations are available. 
1. Ordinary asteroids which have no immediate scientific interest. 
Observations of these should be suspended, but approximate 
ephemerides should be provided for identification purposes, if 
accidentally observed. 
2. Important asteroids of further scientific interest should be observed 
in accordance with prearranged cooperative plans with the object 
of securing sufficient /observations for the scientific purposes in 
hand, and avoiding unnecessary multiplication of observations. 
Ephemerides should be published, the accuracy of the ephemer- 
ides in each case to depend on the research requirements for that 
case. 
Class b. — Asteroids for which accurate definitive elements are available, 
but no general perturbations. 
1. Ordinary asteroids. Same as a (1). Approximate general perturba- 
tions should be computed as a later part of an asteroid program, 
as opportunity presents itself, preferably only the principal terms 
in groups. 
2. Important asteroids. Observations to be dispensed with until 
general perturbations have been computed, degree of accuracy 
to depend on particular scientific requirements in each case, 
then same as a (2). 
Class c. — Asteroids for which satisfactory elements are not available, 
but which have been sufficiently observed for the determination of satis- 
factory osculating elements. 
1. Ordinary asteroids. Same as a (1). Elements to be improved, 
then the same as 6 (1). 
Asteroids for which osculating elements should he derived, with the 
use of special perturbations, accuracy in each case to depend on 
the special research requirements ; then same as h (2) , then a (2) . 
Class d. — Asteroids for which sufficient observations are not available 
for satisfactory orbit determinations. These should be observed accord- 
