304 



SCIENCE 



[N. S. Vol. XXVI. No. 662 



flour out of porscods. Interpreting the 

 simile to suit the present case, it may be 

 said that the accuracy of a quantitative 

 conclusion must depend upon the accuracy 

 of the data upon which it is based. 



For example : it has long been surmised, 

 because of the undoubted periodic relations 

 of the elements, that the atomic weights 

 have some fundamental numerical connec- 

 tion with each other. Many acute thinkers 

 have attempted to discover such relations, 

 and some regularities have indeed been 

 found. Obviously, however, if the data 

 are sometimes as much in error as a whole 

 per cent., nothing but vague conclusions 

 can be drawn from such numerical specula- 

 tions; the time spent upon them is little 

 better than wasted. Before the real 

 numerical relations between the atomic 

 weights can be discovered, it is safe to say 

 that the magnitudes of many of them must 

 be known far more exactly than this. 

 Thus for such speculations the precise de- 

 termination of these physicoehemical con- 

 stants is essential. 



But this ease is only an example of a 

 series of similar eases. In general, it is 

 not an exaggeration to say that in order to 

 obtain the ultimate understanding of the 

 mysteries with which chemistry is con- 

 cerned, all the fundamental data must be 

 determined as accurately as possible. From 

 the point of view of the chemical phi- 

 losopher no pains is too great for deter- 

 mining these data upon which all his really 

 scienti'|ie conclusions m^^st rest. 



Thus it is clear that exact experimenta- 

 tion, instead of being as some of the 

 earlier philosophers supposed incompatible 

 with imaginative impulse and unworthy 

 of a true thinker, furnishes the only basis 

 upon which the imagination has a right 

 to build. No hypothesis which disregards 

 the results of measurement is worthy of a 

 moment's consideration; but given these 



results, fancy may exercise itself at will 

 mthin the limits thus imposed. The re- 

 striction is salutary, because speculation 

 basing itself upon reality is much more 

 likely to reach a useful hypothesis than 

 when unrestricted; and there is plenty of 

 room left for fancy. The quantitative 

 results direct, but do not really hamper 

 imagination. 



These lectures will discuss the theory 

 and practise of exact physicoehemical 

 measurement. It will be shown that much 

 of the uncertainty affecting the present 

 data of physical chemistry is due neither 

 to the variability of the fundamental phe- 

 nomena themselves nor to the inability of 

 the physical methods of measurement to 

 yield constant results, but rather to the 

 superposition of other inessential phe- 

 nomena upon the fundamental ones which 

 it is desired to measure. The discovery 

 and elimination of these inessential phe- 

 nomena, chiefly chemical in their nature, 

 are really the difficult parts of the meas- 

 urement; it is their successful accomplish- 

 ment which makes all the difference be- 

 tween success and failure, and offers a task 

 demanding the ablest knowledge and in- 

 sight, both chemical and physical, theo- 

 retical and experimental. Whether perfect 

 constancy will have been reached when all 

 inessential phenomena have been elimi- 

 nated, no one can certainly say. 



But after all, one may ask, is it worth 

 while in a world filled with burning prac- 

 tical problems demanding speedy solution 

 to expend so much valuable time and 

 energy merely in adding another certain 

 decimal place to a collection of rather dry 

 figures for the sake of abstract scientific 

 learning 1 



When answering such a challenge, in a 

 manner convincing to the practical man, 

 one must recall to mind again the fact that 

 chemistry serves the world in a twofold 



