APEIL20, 1900.] 



SCIENCE. 



609 



according to the generally accepted view of 

 its genesis, was the result of an attempt to 

 provide a mechanical explanation for the 

 solution of a gas by a liquid. Under the 

 influence of some force the particles of the 

 gas are impelled, or diffuse among the par- 

 ticles of the liquid. The same is true of all 

 solutions, the substance going into the solu- 

 tion disappearing as such. And further- 

 more, the solution, when in equilibrium, is 

 homogeneous ; consequently the particles 

 must be very small though they remain 

 discrete, and they must be uniform in mass, 

 volume, and other properties. 



The selection of the historical name atom 

 for the particle did not necessarily imply 

 anything more than has just been given. 

 The apparently ready explanation these 

 views gave for the laws of definite and 

 multiple proportions which Dalton had al- 

 ready advanced, undoubtedly had a pre- 

 ponderating influence in bringing about 

 their general acceptance. It is easy to see 

 that granting the atomic hypothesis, the 

 combination of two substances to form an- 

 other, always identical, must be in definite 

 proportions, or number of atoms or when 

 there are multiple proportions they should 

 bear a simple ratio to one another. But it is 

 not easy to see how the atomic constitution 

 of matter follows, as a necessary, if suf- 

 ficient condition, from the laws of chemical 

 combination, looked at purely objectively. 



It would seem as though the human mind 

 was so constituted that it necessarily de- 

 manded a mechanical explanation of recog- 

 nizable phenomena. Indeed, some of our 

 foremost thinkers apparently insist upon 

 the truth of this proposition, and to Lord 

 Kelvin, if memory serve me correctly, is 

 credited the remark that he finds it impos- 

 sible to understand phenomena for which 

 he cannot construct a mechanical model, 

 meaning mentally, of course. 



It is natural that this feeling should exist. 

 Our earliest impressions are associated with 



mechanical phenomena. These phenomena 

 are intimately connected with our visual 

 and tactual impressions, with just those 

 senses, normally most cultivated, and most 

 closely associated with the logical faculty. 

 All through life a very large proportion of 

 every day experience is with mechanical 

 processes. We thus come to look for the 

 ' mechanism ' of all phenomena of which 

 we become conscious, and when it is not 

 obvious we supply it by analogies from bet- 

 ter known phenomena ; thus the tendency 

 to reduce all phenomena to the lowest 

 terms of matter and the three laws of mo- 

 tion. This leads to the consideration of 

 the Herbartian School, which is hardly 

 within the scope of this paper. The point 

 to be made is that the conception of the 

 atomic constitution of matter to explain the 

 laws of chemical combination is not in itself 

 susceptible of proof, nor in the nature of 

 things is it probable that it ever will be ; 

 and that after all, as we have it to-day, it 

 is nothing more nor less than an analogy 

 with a conceivable mechanical process. 

 This idea has been more or less clearly 

 brought out sometime since by J. J. Thom- 

 son, Mach and others. It has been treated, 

 though not perhaps specifically, by Ostwald, 

 in his now famous paper on the ' Failure 

 of Scientific Materialism,' wherein he very 

 clearly indicates the xiltimate weakness of 

 mechanical explanations of phenomena 

 where they long held sway, instancing the 

 icjnorabmius polemics resulting from the 

 famous address of Du Bois-Raymond ; and 

 more familiar perhaps the development of 

 the theory of light, from the corpuscular 

 theory, through the undulatory theory with 

 its hypothetical ether, demonstrated by 

 Kelvin to be necessarilj' unstable and phys- 

 ically non-existent, to the recent electro- 

 magnetic theory ; and cites Hertz with 

 whose name this theory is so closely asso- 

 ciated as declaring that he saw nothing in 

 it but six differential equations, in an effort 



