88 SCIENTIFIC THOUGHT. 



growth of this conception as apphed not only to the 

 energy of visible and measurable mechanical motion, but 

 to all other forces of nature which have in the course of 

 the century not only been measured in terms of this 

 one quantity, but also represented with more or less 

 success as dependent on the energy of specific forms of 

 motion, be this rotatory or vibratory or translational 

 motion, regular and periodic or irregular and disorderly 

 motion. It is clear that such a general abstract view as 

 Maxwell (first among natural philosophers) took of a 

 special problem was only possible after it had been 

 shown how all physical and chemical actions and effects 

 can be reduced to a common measure. The influence of 

 the development of these views on the kinetic view of 

 nature has been very great. The first and most natural 

 effect of measuring all forces of nature in terms of the 

 energy of motion is to strengthen the kinetic view of 

 natural phenomena. This, however, is not the only view 

 which is possible, or which has been taken, as I shall 

 endeavour to show more fully hereafter. 



The influence of Maxwell's ideas on scientific — nay, 

 even on popular — thought has been very considerable. 

 The main conception around which research, both mathe- 

 matical and experimental, has moved during the last 

 twenty years is the conception of light as an electro- 

 magnetic phenomenon. This view has been much sup- 

 ported and extended by the experiments of Heinrich 

 Hertz, who by ingenious contrivances succeeded in 

 actually exhibiting electro - magnetic waves, and in 

 showing how they differ from light waves merely in 

 length and period, and agree with them so far as 



