CHAPTER XVI 



SOME ADVANCES IN PHYSICAL SCIENCE IN THE 



NINETEENTH CENTURY. ENERGY AND 



THE CONSERVATION OF ENERGY 



About a century after the publication of the Principia, which, by 

 propounding the gravitation formula, raised the ancient and indefinite 

 notion of Attraction to the rank of a useful and rigorously defined 

 expression, another favorite theory [Atomism] of the ancient philoso- 

 phers was similarly elevated to the rank of a leading and useful 

 scientific idea. 



The law of gravitation embraced cosmical and some molar phe- 

 nomena, but led to vagueness when applied to molecular actions. The 

 atomic theory led to a complete systematization of chemical com- 

 pounds, but afforded no clue to the mysteries of chemical affinity. 

 And the kinetic or mechanical theories of light, of electricity and mag- 

 netism, led rather to a new dualism, the division of science into sciences 

 of matter and of the ether. ... A more general term had to be found 

 under which the different terms could be comprised, which would give 

 a still higher generalization, a more complete unification of knowl- 

 edge. One of the principal performances of the second half of the nine- 

 teenth century has been to find this more general term, and to trace 

 its all-pervading existence on a cosmical, a molar, and a molecular 

 scale . . . this greatest of all exact generalizations the conception 

 of energy. 



Electrified and magnetised bodies attract or repel each other accord- 

 ing to laws discovered by men who never doubted that the action 

 took place at a distance, without the intervention of any medium, 

 and who would have regarded the discovery of such a medium as 

 complicating rather than as explaining the undoubted phenomena of 

 attraction. Merz. 



Through metaphysics first ; then through alchemy and chemis- 

 try, through physical and astronomical spectroscopy, lastly through 

 radio-activity, science has slowly groped its way to the atom. 

 Soddy. 



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