508 Dr. D. Mendeleeff [May 31, 



chemical combinations, but with this difference, that the characteristics 

 of the material substances — such as silver, for example, or of any other 

 body — remain unchanged in every subdivision from the largest masses 

 to the smallest particles, and consequently their characteristics must 

 be a property of its particles. But the world of heavenly luminaries 

 appeared equally fanciful at man's first acquaintance with it, so much 

 so, that the astrologers imagined a connection between the in- 

 dividualities of men and the conjunctions of planets. Thanks to the 

 genius of Lavoisier and of Dalton, man has been able, in tlie unseen 

 world of chemical combinations, to recognise laws of the same simple 

 order as those which Cojjernicus and Kepler proved to exist in the 

 planetary universe. Man discovered, and continues every hour to 

 discover ivhat remains unchanged in chemical evolution, and how 

 changes take i^lace in combinations of the unchangeable. He has 

 learned to predict, not only what possible combinations may take 

 place, but also the very existence of atoms of unknown elementary 

 bodies, and has besides succeeded in making innumerable practical 

 applications of his knowledge to the great advantage of his race, and 

 has accomplished this notwithstanding that notions of sympathy and 

 affinity still preserve a strong vitality in science. At present we 

 cannot apply Newton's principles to chemistry, because the soil is 

 only being now prepared. The invisible world of chemical atoms is 

 still waiting for the creator of chemical mechanics. For him our age 

 is collecting a mass of materials, the inductions of well-digested facts, 

 and many-sided inferences similar to those which existed for Astronomy 

 and Mechanics in the days of Newton. It is well also to remember 

 that Newton devoted much time to chemical experiments, and while 

 considering questions of celestial mechanics, persistently kept in view 

 the mutual action of those infinitely small worlds which are concerned 

 in chemical evolutions. For this reason, and also to maintain the 

 unity of laws, it seems to me that we must, in the first instance, seek 

 to harmonise the various phases of contemporary chemical theories with 

 the immortal principles of the Newtonian natural philosophy, and so 

 hasten the advent of true chemical mechanics. Let the above con- 

 siderations serve as m}^ justification for the attempt which I propose 

 to make to act as a champion of the universality of the Newtonian 

 principles, which I believe are competent to embrace every jjheno- 

 menon in the universe, from the rotation of the fixed stars, to the 

 interchanges of chemical atoms. 



In the first place I consider it indispensable to bear in mind that, 

 up to quite recent times, only a one-sided affinity has been recognised 

 in chemical reactions. Thus, for examjile, from the circumstance 

 that red-hot iron decomposes water with the evolution of hydrogen, 

 it was concluded that oxygen had a greater affinity for iron than for 

 hydrogen. But hydrogen, in presence of red-hot iron scale, appro- 

 priates its oxygen and forms water, whence an exactly opposite 

 conclusion may be formed. 



During the last ten years a gradual, scarcely perceptible, but 



