APPENDIX I. 455 



division from the largest masses to the smallest particles, and consequently 

 these characteristics must be properties of the 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 

 individualities of men and the conjunctions of planets. Thanks to the genius 

 of Lavoisier and of Dalton, man has been able, in the unseen world of che- 

 mical combinations, to recognise laws of the same simple order as those 

 which Copernicus and Kepler proved to exist in the planetary universe. Man 

 discovered, and continues every hour to discover, what remains unchanged 

 in chemical evolution, and how changes take place in combinations of the 

 unchangeable. He has learned to predict, not only what possible combina- 

 tions may take place, but also the very existence of atoms of unknown elemen- 

 tary substances, 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 che- 

 mical 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 experi- 

 ments, 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 considerations serve as 

 my 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 com- 

 petent to embrace every phenomenon 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 example, from the circumstance that red-hot iron de- 

 composes 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, appropriates its oxygen and forms water, whence an 

 exactly opposite conclusion may be formed. 



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

 important change has taken place in the views, and consequently in the 

 researches, of chemists. They have sought everywhere, and have always, 

 found, systems of conservation or dynamic equilibrium substantially similar 

 to those which natural philosophers have long since discovered in the visible 

 world, and in virtue of which the position of the heavenly bodies in the 

 universe is determined. There where one-sided affinities only were at first 

 detected, not only secondary or lateral ones have been found, but even those 



