man of science, appear to me to be scarcely worthy of being regarded as 

 even an approximation to the solution of the problem. I pass over also 

 for other reasons the speculations of Newton, Boscovich, and others ; 

 and I come to the latest suggestion of all,* namely, that of Sir William 

 Thomson, which is, that " what we call matter may really be only the 

 rotating portions of something which fills all space ; that is to say, 

 vortex-motion of an everywhere present fluid." To say that a suggestion 

 is made by Sir William Thomson is to say that it is worthy of all conside- 

 ration from scientific men ; and to such a jury, rather than to the mixed 

 audience which I have the honour to address to day, I should be dis- 

 posed to leave the determination of the value of the suggestion concern- 

 ing matter which I have just now quoted. In truth, it would be im- 

 possible for me, on an occasion like this, even to put before you some of 

 the considerations, upon which alone any solid opinion could be formed ; 

 but what I wish to bring under your notice is this, that the hypothesis in 

 question concerning matter postulates " something which fills all space." 

 What can that something be ? If it be not matter, what is it ? I do not 

 say that it does not exist, though the actual conception of something 

 filling all space is manifestly impossible to the human mind ; the thing 

 may however be assumed for argument's sake to be capable of existence, 

 though, in consequence of an inherent infirmity of the mind, this exist- 

 ence may not be thinkable. But granting all that can be required for 

 the purpose of making Sir William Thomson's hypothesis a possible one, 

 do we really do more than drive back the existence of matter one step 

 further ? Do we do more than arrive at the conclusion, that matter is 

 something, which is something else under certain peculiar conditions ? 

 Is not the all pervading fluid merely the raw material, out of which is 

 formed by vortex-motion those atoms of which Professor Clerk Maxwell 

 speaks as having much of the character of " manufactured articles"? 



You will quite understand that I am by no means desiring to speak 



lightly of this hypothesis. Professor Tait says,t " With a little 



further development the theory may perhaps be said to have passed its 



first trials at all events, and, being admitted as a possibility, left to time 



* "Recent Advances in Physical Science," p. 290. + Do., p. 300. 



