in a Programme of Physics. 459 



and determine the logical value of the abstract unity sought 

 by physicists. 



But physics, as at present studied, has reference solely to 

 the general forces or agencies of nature. We must add to 

 this a higher and more philosophical regard. The science of 

 energy treats of an activity which is in itself immutable, and 

 in the unity of its object belongs to nothing that is partial or 

 transitory. 



II. The Idea of Energy as compared with the actual state of 

 Physics. — The idea of energy agrees with our idea of physics, 

 including the fundamental parts of chemistry and mechanics. 

 Not unfrequently in the recent history of physics have we seen 

 that science ascertaining the relations between individual facts 

 or forces, and, these transcending, rise to their approximate 

 source. Mechanics and chemistry have sometimes manifested 

 strict relations, despite their independence and difference of 

 method and object. The former being the general doctrine 

 of motion, and the modelling under which energy displays 

 itself, has to determine step by step the different positions of 

 activity ; hence its customary separation from the latter is 

 scarcely real or effective. Chemistry certainly shows a very 

 different aspect from that of physics, as a history differs from 

 a philosophy ; yet when we enter the field of chemical affi- 

 nity, we must admit that to be part of the domain of energy. 

 The revolution which has taken place in modern physics 

 has been distinctly in favour of unification, and would never 

 have been accepted without a tacit faith in the new ruler. The 

 researches of Fleming on the contact theory of electricity, and 

 of Becquerel on electro-capillary phenomena, which at first 

 seemed to controvert the splendid labours of Faraday, have 

 since been harmonized therewith ; but, in the verifying pro- 

 cess, we have been compelled to take into account the bearing 

 of thermodynamics and mechanics on the various results. 

 Crookes has brought into prominence, in connexion with 

 another order of forces, the intimate connexion between gra- 

 vitation, light, and heat. Volta has shown the relation of heat 

 to the electromotive forces of differing couples. Holzmann 

 has determined the dielectric constants of insulators. Merget 

 has succeeded in reproducing with powders and pulverulent 

 bodies the phenomena of thermo-diffusion exhibited by vege- 

 table organisms. Edlund's theory of electricity has thrown a 

 most vivid light on all that was obscure in that branch of 

 knowledge. Thermodynamics has lent aid to a vast number 

 of questions not pertaining simply to heat. 



What physics represents at the present time, may be best 

 observed by ascertaining some of its precedents, and following 



