42 ORGANIC EVOLUTION CONSIDERED 



It occupies all space except that occupied by 

 atoms of matter. 



It must be capable of transmitting light at the rate 

 of about 186,000 miles per second. 



It must offer almost no resistance to the motions 

 of the heavenly bodies, for we know that the earth 

 has been moving through it for millions of years 

 without having its motion destroyed — it is now mov- 

 ing at the rate of about 19 miles per second. 



It must be non-condensible by gravity, for if it 

 could be thus condensed, as can our atmosphere and 

 all other gases, it would be too rare in interstellar 

 space to transmit radiant energy by transverse vibra- 

 tions. This makes it necessary to assume that it is a 

 continuous substance, i. e., that there are no vacant 

 spaces between the atoms of ether, unless it should 

 be assumed that it is a substance which is free from 

 gravity. With freedom from the effects of gravity 

 we might imagine ether to be uniformly distributed 

 through all space, and composed of molecules that 

 are not in contact, i. e., that ether is porous. 



However this may be, ether must possess great 

 rigidity compared with its density in order that it may 

 transmit transverse vibrations. 



It must be capable of receiving and transmitting 

 the vibrations of the atoms and molecules of ordin- 

 ary matter. The different kinds of heat and light 

 represent different rates of vibration of atoms and 

 molecules. Radiant energy displays the activity of 

 atoms and molecules, — in dealing with it we have to 

 do with the properties of elements. 



The spectroscope reveals the fact that in studying 

 light we gain a knowledge of the qualities of the 

 atoms of matter. Light might be called the music 

 of vibrating atoms. White light is the perfect har- 

 mony of all the vibrations of light. 



