tiation of the etherial substance in a definite direction, a rliythmic dis- 

 turbance of its homogeneity by the formation of volumes or spheres of 

 tension in alternation with volumes or spheres of laxity, tension and 

 laxity successively changing places or regularly succeeding in lines 

 radiating from its source, in a manner analagous to sound-waves, which 

 <;onsist of alternate successive spheres of condensation and rarefaction 

 in the gaseous atmosphere or other conducting medium. 



Now the motions of the atoms of the several elementary substances, 

 differing as they do one from the other, differ, it is fair to assume, in at 

 least two respects, viz , first in their rates or periods of vibration, that 

 is, in the frequency with which, in a given time, they change shape by 

 the back and forward swingingof their proper substance; and second in 

 their mode or path of vibration, that is, in the figures which a point in 

 their respective surfaces describes in space during a complete vibration. 

 The term vibration is here used in the most general sense to designate 

 any and every form of recurring or cyclic movement, reciprocating mo- 

 tion in straight lines, rotation, revolution, and every conceivable com- 

 pound of two or more of these. 



We can study molecular motions under the three known conditions 

 of matter: gaseous, liquid and solid. A rapid glance at the facts in- 

 volved in chemical reactions, both synthetic and analytic under these 

 several conditions, will discover indications which, while not conclusive 

 on the subject, tend strongly to support the proposition that combining 

 attractions depend on compatibility of motions as herein affirmed. 



The molocules of matter in a gaseous state may be regarded as in a 

 semi-chaotic condition with a tendency to separate, rather than to 

 aggregate; their excursive motions in more or less straight lines are 

 immeasurably greater in extent than any proper self centred vibratory 

 movements they may execute. Moreover, as the direction of their 

 excursion lines is determined largely by impact and reflection, the ele- 

 ment of accident or irregularity is more or less involved. These condi- 

 tions cannot a priori be considered favorable to composition or coales- 

 cence of varying motions. And as a matter of fact, mixed gases do not 

 ■combine easily nor rapidly (and sometimes they refuse to combine) 

 under ordinary conditions. The oxygen and nitrogen of our atmos- 

 phere remain constantly and persistently distinct, except as a result of 

 the special action of outside agents, as e. g. an electric discharge, etc., 

 "Chlorine and hydrogen gases, while they do slowly and gradually com- 

 bine even in the dark, need the influence of the sun's rays, or those of 

 the electric light, to produce a rapid union; so with oxygen and hydro- 

 gen; and many others might be cited. Observe that in all these cases 

 the special agent — the critical factor — determining the union, is some 



