I'UESIDKXTIAL ADDRESS SECTION A. 35 



Newton was not the inventor of the steam engine or \\ireless 

 telegraphy, but he prepared the human mind so that others M'ere 

 able to do that. 



Another way by which the law of gravitation exerted its 

 intluence upon the development of science was in stating actions 

 at a distance. TJiis meant a revolution in the views of those 

 times. Until then, only actions of contact, such as pressures, 

 tractions, etc., were known. Due to the views of Newton, a 

 dualism appeared : actions of contact and actions at a distance. 



The physicist does not like dualisms. But it was not easy to 

 reject the hypothesis of Newton, for his law not only gave a fair 

 account of the observed movements, it also harmonised with the 

 idea of a free space, homogeneous and isotropic, because the 

 statement of a variation of the action inversely proportional to 

 the square of the distance showed that gravitation spreads 

 vmiformly in all directions and is uniformly distributed upon the 

 surface of a sphere, its total intensity being constant whatever 

 may be the radius of the sphere. 



In order to avoid the dualism, physicists were inclined to 

 regard actions of contact as actions at a distance (distance very 

 minute, of course). Bodieis were regarded as formed by very 

 minute particles which exercised between themselves actions at 

 a- distance. 



This way of regarding the constitution of matter (which 

 later was to give chemists the idea of the atomic theory) caused 

 physico-mathematics to be bom; physico-mathematics is, as the 

 M^canique Celeste," a daughter of the law of gravitation. 



Later on, physico-mathematics evolved and is nowadays a 

 science very different from the " M^canique Celeste." It should 

 not be forgotten, however, that, if the principle of gravitation is 

 not at present directly applied to the mathematical treatment of 

 physical phenomena, other principles are applied, some of which 

 are derived from it, in the former phases of this branch of science. 



Physics and chemistry have nowadays a tendency to be 

 merged in a single science through the present ideas on the 

 constitution of the atom, of which you heard a good explanation, 

 a year ago at Durban, by one of the pioneers of the new theory. 

 Dr. Moir. The time seems not far distant when chemical 

 phenomena may be treated mathematically, as are physical ones, 

 through the movements of electrons. 



It is already believed that electrons go round the nucleus 

 of their atom and it was astronomy that gave the model for those 

 movements, as it is assumed that they keep a planetary motion. 

 This assumption gives a fair account of some facts as, for example, 

 the features of some spectra. 



. Thus, it was the law of gravitation, originally due to the 

 skilful observations of Tycho Brahe, that gave the directive and 

 strongest impulses to scientific investigations. 



