THE ATOMIC THEORY. 261 



their partial!}^ displaced neigh])ors. These surfaces arc wavc-Uke in 

 character and constitute what we recognize as ordinary' matter. 

 Where they exist there is a local deticiency of mass, so that matter is 

 less dense than its surroundings; and this, as Heynolds has said, 

 is a complete inversion of the ideas which we now hold. Matter is 

 measured by the absence of the mass which is needed to complete a 

 normal piling of the grains in the medium. In other words, it might 

 be defined as the defect of the universe. The ''singular surfaces" 

 already mentioned are molecules, which may cohere, but can not pass 

 through one another, and they preserve their individuality. 



Possibly I may misapprehend this theory, for it has been published 

 in a most concise form, and the reasoning" upon which it rests is not 

 g'iven in detail. I can not criticise it, l)ut 1 may offer some sugg-es- 

 tions. If matter consists of weaves in a universal medium, how does 

 chemical union take place '. Shall we conceive of hydrogen as repre- 

 sented by one set of waves and nitrogen as represented b}^ another, 

 the two differing onh^ in amplitude!' If so, when they combine to 

 form annnonia there should be either a superposition of one set upon 

 the other, or else a complex system might be found showing interfer- 

 ence phenomena. But would not the latter supposition imply a 

 destruction of matter as matter is defined by the theory^ Could one 

 such wave coalesce with or neutralize another '\ To conceive of a union 

 of waves without interference is not eas}^, but the facts of chemical 

 combination must be taken into account. When we remember that 

 compoiuids exist containing- hundreds of atoms within the molecule, we 

 begin to realize the difficulties which a complete theory of matter must 

 overcome. Chemical and physical evidence must be taken together; 

 neither can solve the problem alone. At present the simplest concep- 

 tion for the mind to grasp is that of an aggregation of particles. 

 Beyond this all is contusion, and mathematical devices can help us 

 only a little. In speaking thus I assign no limit to the revelations of 

 the future; some theor}', now before the world, ma}" prove its right 

 to existence and survive; l)ut none such, as yet, can be taken as defi- 

 nitel}' established. The theory which stands the test of time will not 

 be a figment of the imagination; it nmst be an expression of o))served 

 realties. But enough of speculation; let me, before I close, say a few 

 words of a more practical cliaracter. 



Dalton's statue stands in Manchester, a fitting tribute to his fame. 

 But it is something which is finished; something on which no more 

 can be done; something to be seen onh' by the few. As a local 

 memorial it serves a worthy purpose, l)ut Dalton's true monument is 

 in the set of constants which he discovered, and which are in daily 

 use by all chemists throughout the world. Here is something that is 

 not finished; and h(M-e Dalton's memory can be still further honored, 

 by good work, good research, honest efforts to increase our knowledge. 



