72 PHYSICS OF MATTER 



This intellectual character of scientific research is well illustrated 

 in the enthusiasm which marked the news of Hertz's discovery of 

 electromagnetic waves. The facts observed might easily have been 

 thought to be in themselves insignificant : a slight spark observed 

 between the ends of a bent wire near a discharging electrified system. 

 There was no thought of a practical application, and yet a wave of 

 almost unprecedented excitement spread among physicists the world 

 over. Nor was it alone admiration for the skill, the insight and grasp 

 of the great experimenter that won the victory, though this had its 

 effect. It was mainly an exultant enthusiasm over the triumph of 

 an idea, the unification of science in the confirmation of Maxwell's 

 great theory. 



It is clear, then, that physics may react on the other sciences in a 

 variety of ways, in its methods and appliances, in its discoveries, and 

 in its ideas and generalizations; and it is evident, therefore, that we 

 must limit ourselves to a brief consideration of certain phases of the 

 subject. I have, therefore, chosen to present very briefly some con- 

 siderations relative to theories of matter, for here physics and chem- 

 istry come into the closest contact; also to touch upon some other 

 relations of chemistry and geology to physics, that are of particular 

 interest at this present time. 



The fundamental problem in the physics of matter is the nature 

 of matter itself. Of course we recognize at the outset the limitations 

 that bound our attempts at a solution. We may hope to reach event- 

 ually some conclusion as to the structure of matter, whether homo- 

 geneous or molecular or grained, also as to the relative motions of the 

 parts of the molecule and the law of variation of force between them 

 with the distance. But if we seek to go farther and explain the 

 forces acting in and between molecules in terms of what appear to 

 be more simple and general laws, it seems inevitable that a medium 

 must be assumed, the properties of which will depend on what is 

 assumed as a primary postulate. If we accept, as is usually done, 

 the postulate that forces in their last analysis can only be explained 

 when referred to pressures exerted between contiguous portions of 

 some underlying medium, it seems probable that a theory must be 

 adopted something like the vortex atom theory of Lord Kelvin, 

 with its continuous, incompressible, perfectly fluid medium in which 

 vertically moving portions constitute the atoms, or Osborne Rey- 

 nolds's theory of space as filled with fine hard spherical grains, in 

 which, regions with nonconformity in arrangement, are the atoms 

 of ordinary matter. Though it must be said that the assumed hard- 

 ness of the ultimate spherules in the latter theory is a property 

 which in itself needs explanation. 



Perhaps, however, in laying down the postulate mentioned above 

 we are pushing too far inferences from our superficial experience. 



