56 THE WORLD-ENERGY 



This remarkable paragraph, in which the identity 

 between matter and force is fairly asserted, concludes with 

 the statement that " To our chapter on the ' Properties of 

 Matter ' we must refer for further discussion of the ques- 

 tion, What is matter 9 " 



The part of the joint work of these two physicists con- 

 taining the promised chapter on the properties of matter 

 does not seem to have appeared. But a volume under 

 that title has been published by Professor Tait, while Pro- 

 fessor Thomson has also separately developed his own 

 theory upon the subject ; from which it may be guessed 

 that the two could not entirely agree as to what should 

 be said upon this particular theme. 



Indeed, after certain introductory remarks, Professor 

 Tait declares (p. 11) that these "have been brought in 

 with the view of warning the reader that we are dealing 

 with a subject so imperfectly known, that at almost any 

 part of it one may pass by a single step, as it were, from 

 what is acquired certainty to what is still subject for mere 

 conjecture." To which he adds that : 



"An exact or adequate conception of matter itself, 

 could we obtain it, would almost certainly be something 

 extremely unlike any conception of it which our senses 

 and our reason will ever enable us to form." 



A little further on (p. 14) this declaration of nescience 

 on the part of the scientific man concerning matter is even 

 more emphatically set forth. He has been indicating the 

 various theories concerning the constitution of matter, and, 

 referring especially to W. Thomson's theory of vortex atoms, 

 declares that this "has the curious peculiarity of making 

 matter, as we can perceive it, depend upon the existence 

 of a particular kind of motion of a medium which, under 



