932 



SCIENCE. 



[N. S. Vol. IV. No. 104. 



wliicli have become separated. A reunion, 

 since a separation, which does not date 

 from a very early period, took place. New- 

 ton, the Father of modern physics, wished to 

 apply his law of force to cosmic phenomena 

 as well as to chemical. Even at the begin- 

 niDg of this century we find men like 

 Dalton, Wollaston, Ampere, Davy, Dulong, 

 Gay Lussac and others, who have simul- 

 taneously enriched both physics and chemis- 

 try. The separation came later and we 

 recognize Weber, Helmholtz, Kirchhoff, 

 Clausius, Fr. Neumann, Kundt, Hertz, as 

 distinctly physicists, while Berzelius, Du- 

 mas, Liebig, Wohler, Hofmann, are as dis- 

 tinctly chemists. It is also true that there 

 were a few, contemporary with the above 

 named, whose work enriched both physics 

 and chemistry, notably, Faraday, Hittorf, 

 Horstmann, J. W. Gibbs and the cooperation 

 of Kirchhoff and Bunsen, and Guldberg and 

 "Waage. But that a marked separation of 

 physics from chemistry had taken place is 

 beyond question. 



The time at which this began to be pro- 

 nounced was about the year 1835. A de- 

 cided tendency to reunite was observed in 

 the year 1885. It was at this latter date 

 that van't Hoff's epoch-making work on 

 solutions appeared, and in the same year 

 Ostwald published the first volume of his 

 Lehrbuch. Since that time the number of 

 those who are at once physicists and chem- 

 ists has greatly increased. 



If we ask what is the difference between 

 physics and chemistry it is generally re- 

 plied that chemistry has to do with the 

 composition and structure of the molecules, 

 while physics deals with the molecules 

 already made, but this distinction is 

 founded on a special hypothesis, the atomic 

 hypothesis, which cannot be regarded as a 

 general principle on which to base such a 

 division. If we state that physics investi- 

 gates those natural phenomena in which 

 the properties of matter remain unchanged, 



while chemistry studies the transformations 

 of matter, the distinction does not always 

 agree with the facts. 



On the other hand, physics and chemistry 

 have much in common which is distinctive. 

 The other branches of natural science find 

 the objects of their investigations existing 

 in the external world. The zoologist, the 

 physiologist, the astronomer, have their 

 material already prepared for them. Their 

 work is descriptive. The chemist and 

 physicist prepare their own materials, and 

 their science is constructive. But what 

 is the real difference between physics and 

 chemistry, which are taught in separate 

 laboratories and by specialists in each 

 branch? The distinction is one which is 

 deeply imbedded in the mind of the inves- 

 tigator. He who would become a physicist 

 must acquire a good mathematical training, 

 while a chemist must be acquainted some- 

 what w4th mineralogy, physiology and 

 botany. Further, it is difficult to preserve 

 physical apparatus in the presence of the 

 destructive fumes of the chemical labora- 

 tory, and consequently such apparatus is 

 usually absent from, or in poor condition 

 in, the chemical laboratory. For the same 

 reason the physicist avoids the ' chemical 

 kitchen' in his apartments. Thus the dis- 

 tinction which existed between physics 

 and chemistry for a half-century (1835- 

 1885) was a necessity and contributed 

 largely to the advance of our knowledge 

 of the natural sciences. And those same 

 causes which have made the separation of 

 physics from chemistry a necessity are 

 still operative to some extent, so that no 

 one thinks at the present day of combining 

 the physical and chemical laboratories into 

 one. But like two great nations which 

 have been brought more closely together 

 by common interests, physics and chemistry 

 will have more and more points in common 

 the further investigation is carried. Physi- 

 cal chemistry is the diplomatic agent to 



