Structure of the Universe 389 



water, or 480 times denser than platinum, which is the densest matter 

 on earth. 



In view of this great density of the medium of space, does it not 

 seem rather paradoxical that what we call matter, that is, the planets, 

 suns, moons, comets and so forth, which are so much less dense than 

 the medium should move through the medium apparently without 

 resistance and at such high velocities? Our earth, as you know, 

 moves in its orbit at a velocity of 19 miles per second. You have 

 all seen bubbles moving in water. Reynolds shows that the earth 

 a,nd all the other material bodies move through space in a similar 

 manner. They are less dense than the medium in which they exist, 

 and, as we shall see, their movements are due to differences of pressure 

 in the surrounding medium. They are like so many filmy soap 

 bubbles which a child blows from the stem of a pipe. Real mass is 

 not in the material things which we see, but in space where the eye 

 sees nothing. The sober conclusion of the most advanced dynamical 

 science is that matter is a negative thing so far as its mass is con- 

 cerned, and that the space occupied by "matter" contains very much 

 less mass than the space where no "matter" exists. 



Is the Medium Continuous or Granular? 



We now come to another important point, I have here on the 

 table a glass full of small shot and another glass full of jelly, The 

 glass of shot we will take to represent a universe composed of what 

 we will call a "granular medium," that is, a medium composed of dis- 

 crete or separate parts or grains; the jelly represents a universe com- 

 posed of what we will call a "continuous medium," that is a medium 

 not made up of. discrete or separate parts, but continuous in its struc- 

 ture. These two kinds of structures represent the two views which 

 are held as to the nature of the structure of the medium of space. 

 We have ascertained that this medium is very dense; now let us en- 

 deavor to find out the character of its structure. On the correct 

 answer to this question hinges the true solution of the problem of 

 gravitation. ! 



We have had atomic systems of philosophy from the earliest ages, 

 Democritus and Lucretius are the ancient fathers of the atomic sys- 

 tems. In his great poem on the origin of things Lucretius speculates 

 on the atomic system of the universe, and tries to show that the origin 

 of the universe was due to a "concourse of atoms," There have been 

 many speculations on this point from that day to this; but it has 

 remained for modern science, with its experimental and mathematical 

 methods, to arrive at the truth. 



Analogy would suggest that the medium of space would be gran- 

 ular in its structure. We are not acquainted with anything that can- 

 not be divided into parts. The atomic theory in chemistry, whose 

 modern founder was Dalton, and which has proved so fertile, postu- 

 lates that the chemical unit is the atom, and that the atom is the 

 unit from which is built up systems of molecules, organic and inor- 

 ganic, in the universe around us; that all things are combinations and 

 compounds of atoms. The atom, indeed, has been weighed and meas- 

 ured. Maxwell and Kelvin did this for us, and we know in fact 



