210 GENERAL PHYSIOLOGY 



like the atoms in the molecule and the molecules in the mass ; 

 since Newton's immortal discovery it has been known that the 

 paths of the heavenly bodies result from the mutual attractions of 

 their powerful masses. This mass attraction, which binds the earth 

 to the sun, and the moon to the earth, and compels a stone thrown 

 upward to return again to the earth, is gravity or the energy of 

 gravitation. Finally, thermal, photic, electrical, and magnetic energy 

 are the forms of energy that put the atoms of the hypothetical 

 ether, which fills universal space and penetrates all bodies, 

 into those forms of motion termed heat, light, electricity and 

 magnetism ; for in accordance with the researches of modern physics 

 the phenomena of heat, light, electricity and magnetism result 

 merely from the vibrations of very minute particles. 



But simple reflection shows that these forms of energy are 

 not equivalent and separate. If all matter, including the 

 hypothetical ether, is composed of atoms as its smallest physical 

 particles, and if nothing corporeal exists beyond matter, all forms 

 of energy, since they are associated with matter, must have their 

 seat in atoms. In other words, atoms are the smallest particles 

 endowed with energy, and it is evident that the forms of energy 

 that are assumed for the motions of masses, such as gravity, must 

 have their seat in atoms. Now, a priori, it is in the highest degree 

 improbable that every atom is provided with eight different forms 

 of energy. Scientific experience, which shows that everywhere in 

 nature apparent multiplicity can be traced to unity, suggests that 

 all these different forms of energy may be traced to a single form. 

 As a matter of fact, molecular and mechanical energy and energy 

 of gravitation, upon the one side, have been put into close relations 

 with one another, as well as thermal, photic, electrical and magnetic 

 energy upon the other side ; and very recently electro-chemical re- 

 searches have made it appear that a very close relation exists 

 between chemical and electrical energy. Hence we have a well- 

 founded hope that before very long physics will succeed in demon- 

 strating all forms of energy to be merely the expression of one and 

 the same form, which appears different under different conditions ; 

 just as chemistry hopes to be able sometime to reduce the multi- 

 plicity of the chemical elements to the properties of a single 

 original element, perhaps the universal ether. 



The probability that the different forms of energy are only 

 different modes of appearance of one and the same energy, amounts 

 almost to a certainty in the light of the fact that one form of 

 energy may be changed into another form, and in nature is con- 

 tinually so changed. As is well known, this all-important fact 

 finds expression in the law of the conservation of energy, which was 

 discovered and founded by Robert Mayer and Helmholtz, and which 

 has become the foundation of our whole modern view of nature. 

 This fact is explicable only in accordance with the idea that energy 



