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.