8 MORRIS LOEB 



of affinity and reaction which cannot be explained by merely 

 paraphrasing the phenomena? Not merely book-learning 

 may be acquired by this knowledge; it continually furnishes 

 us with new weapons for the further investigation of truth. 



Gentlemen, the interest in general and physical chemistry 

 is reawakening, and we may soon hope to see these studies as 

 prominent as they were in the times of Humphry Davy and 

 Gay-Lussac, of Berthollet and Dalton, of Berzelius and of 

 Michael Faraday. I am thankful that this new university 

 has granted me an opportunity of calling attention to them 

 in our country; and I shall be happy indeed if I can augment 

 in you the love for this branch of speculative philosophy, 

 by pointing out some recent achievements and showing how 

 much still remains to be done. 



Confronted with the necessity of defining the scope of 

 chemistry, I would say: Chemistry is that branch of Physics 

 which treats of the differentiation of matter. Treading gin- 

 gerly on the dangerous ground of metaphysics, we may re- 

 cognize that there are four principles to which the educated 

 mind refers natural phenomena, four first causes, four 

 categories, four systematic axes, namely: energy, matter, 

 space, and time. The practice of referring all outward im- 

 pressions to these ultimate principles is undoubtedly a great 

 advance over the assumption of the cruder "elements" of 

 the Middle Ages, earth, air, fire, and water; but even energy, 

 matter, space, and time are not by any means ideas to which 

 we attach a definite, unalterable meaning. Their definition 

 seems to vary in different minds and at different times in the 

 same mind. Some prefer to consider time a mode of space, 

 and others consider both time and space attributes of matter 

 and energy, but not as independent essentials. All that we 

 can say of energy and matter is that they exist, at least to 

 our perceptions. We are apt to consider matter as some- 



