KINETIC OR MECHANICAL VIEW OF NATURE. 39 



matters, that at the present moment he knows as little 

 as to the true nature of these agencies or substances as 

 he did fifty years ago. 1 



Viewed from the position which we occupy in this 

 history of thought i.e., in relation to the development 

 of ideas the conception of an ether has, however, like 

 the atomic theory, had the most marked influence on 

 scientific research and reasoning. In digging for a hidden 

 treasure, in trying to describe the atoms or the ether, 

 many practically useful conceptions, applicable to tangible 

 phenomena, have been discovered. The atomic theory 

 led at once to an enormous increase of our knowledge of 

 different forms of matter, the knowledge of the elements, 

 and of their innumerable possible compounds. The con- 

 ception of the ether has led similarly to an enormous ex- 

 tension of knowledge of the different possible forms of 

 motion. It is in this sense that we are greatly indebted 

 to these abstract conceptions : both have guided our ideas 

 in trying to understand and grasp the endless variety 

 of phenomena. Let us see how from the early years 

 of the undulatory theory of light our knowledge 

 regarding the different forms of motion has grown, how 

 that theory has contributed to the kinetic view of nature. 



1 Lord Kelvin, in referring to | first session as professor. Some- 

 fifty years of scientific labour, said thing of sadness must come of 

 (see the publication by James failure ; but . . . what splendid 

 Maclehose & Sons of the proceedings compensation for philosophical fail- 

 at his jubilee in 1896, p. 70) : " I ! ures we have had in the admirable 

 know no more of electric and , discoveries by observation and ex- 

 magnetic force, or of the relation periment on the properties of 

 between ether, electricity, and matter, and in the exquisitely 

 ponderable matter, or of chemical beneficent applications of science 

 affinity, than I knew and tried to to the use of mankind with which 

 teach' to my students of natural these fifty years have so abounded." 

 philosophy fifty years ago in my ' 



