390 Structure of the Universe 



aoout how many atoms could be laid alongside each other in the length 

 of an inch. They tell us that from ten million to one hundred mil- 

 lion atoms could be laid alongside each other to make up an inch in 

 length. Of course, anything so small as this is inconceivable; but we 

 know that the inconceivability of a thing now-a-days does not mean 

 that it is impossible. Kelvin stated that if a drop of water were en- 

 larged to the size of the earth, which we know is about 8,000 miles 

 in diameter, the atoms or molecules of which it is composed would 

 appear about the size of base balls. 



In recent years, however, somethng very much smaller than the 

 atom has been discovered by science. You have all heard of the elec- 

 tron. An electron is an atom of electricity. It is now maintained by 

 physicists that the ordinary chemical atom which I have just spoken 

 of, is a compound thing, and is composed of aggregations of thou- 

 sands of electrons. An electron has been defined as an "electric 

 point charge" in the ether. It seems to be an almost infinitely small 

 point of electricity, and the idea is that aggregations of these electric 

 point charges or electrons, when combined into a system form what is 

 known as the chemical atom. Configurations of such a system have 

 been worked out by Thomson, Larmor and others, and it would ap- 

 pear that the system of the chemical atom which is an aggregation 

 of electrons is far more complicated than the Golar system. The in- 

 finitely small is turning out to be more complex than the infinitely 

 great. The universe within the atom seems to be more complicated 

 than the universe outside. The electron is, of course, very much 

 smaller than the atom, and, like the atom, its size is inconceivable. 

 One may get an idea of the size of the electron as compared with 

 the size of the atom if we suppose the electron to be about as large 

 as the head of a pin revolving inside the Minneapolis Auditorium* 

 the Auditorium being taken to represent the size of the atom. 

 These electrons which make up the atomic system -move with very 

 high velocities in the atomic system. The mass of the moving elec- 

 tron has been measured, as well as the electric charge which it car- 

 ries. 



So we see that by the discovery of the electron we have simply 

 discovered a smaller kind of atom than the old chemical one. The 

 electron theory, then, still maintains the granular structure of the 

 ether or medium of space. I ought to say, however, that there are, 

 still some physicists, notably, Sir Oliver Lodge, who seem to main- 

 tain that the medium of space is not granular or of a discrete struc- 

 ture, but that it is a "perfectly continuous, incompressible and inex-- 

 tensible medium filling all space without interstices or breach of con- 

 tinuity." The continuous mediuip theory, however, has so far com- 

 pletely failed to give the slightest clue to the cause of gravitation, 

 and all that Lodge has to say is that "gTavitation is explicable by. 

 differences of pressure in the medium, caused by some action between 

 it and matter not yet understood." He is right in saying that it is 

 caused by differences of pressure in the medium, but he cannot find 

 the proper' mechanism to produce these necessary differences of 

 pressure in his continuous medium. 



By an elaborate analysis Reynolds shows that the medium of space 



