mode of motion introduced: some etherial wave-force adding to or 

 changing in some way the motions of one or both of the combining 

 molecules. 



In the solid state, too, the conditions favorable to molecular changes^ 

 either of combination or decomposition, are absent in sti*ll greater degree; 

 the distances between atom and atom or between molecule and molecule 

 being inconsiderable when compared with the line or orbit of vibration 

 and size of particles. As a matter of fact, the solid state does not present 

 many striking examples of chemical reaction except at the surface. In 

 this state, inasmuch as amplitude of vibration is reduced to a low degree^ 

 the introduction of diverse elements is not easy. Even when such 

 rough mechanical mixture as we can secure by trituration is made, the 

 distance separating the little masses of the mixture are immeasurably 

 larger than those necessary for atomic combination. At the surfaces 

 where the molecules are free in some cases to make limited excursions 

 into the vaporous or gaseous atmosphere surrounding them; and the 

 atmosphere is perhaps condensed, combinations take place easily 

 enough in some cases; iron rust, silver sulphuret, copper oxides and 

 carbonates, and others will at once suggest themselves as examples. 



With substances in liquid solution, or rendered fluid by heat, the 

 conditions favoring chemical changes seem to be the best possible. 

 The most unfettered motion in every direction throughout the mass; 

 nothing in the way of accident (as in gases) to disturb the natural and 

 proper rhythm of the atoms or molecules. The waves formed in the 

 ether pervading the intermolecular spaces of a mixture in solution of 

 compatible atoms, present to the eye of the imagination a picture of the 

 most beautiful and regular, though intricate tracery. Along these 

 variously curving lines, paths of least resistance, it is possible, and de- 

 lightful to the philosophic mind, to picture the atoms having pfhnity, 

 moving and uniting with their complimentary atoms to form molecules, 

 which, continuing to swing with the double or multiple force and com- 

 posite motion, speed along the etherial paths in figures of still greater 

 intricacy and beauty. 



Hastening to a conclusion of this attempt to sketch a theory of 

 chemical attraction ; let me say that, as we judge of the truths of 

 hypotheses largely by their correspondence with other accepted hy- 

 potheses, and by the number of phenomena which they "explain" or 

 bring under a broader generalization; I shall attempt to show such cor- 

 respondence and such power in this. Only a few of the phenomena in 

 the domain of chemistry, which, by this theory are shown to be regular, 

 while formerly considered anomalous, can be indicated. And first 

 catalysis, or the action of presence, e. g. manganese dioxide, used in 

 the reaction for procuring oxygen from potassium chlorate. Here*, 



I 



