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XXX. Of the Kinetic Theory of Gas, regarded as illustrating 

 Nature. By Geokge Johnstone Stoney, M.A., D.Sc, 

 F.R.S., Vice-President, Royal Dublin Society*. 



SCIENCE may be defined as the investigation of how 

 nature works, of how and why events in nature occur. 



This investigation is best carried on by employing the 

 Physical Hypothesis, viz., that the objects of nature act on 

 one another, either directly (action at a distance), or through 

 intervening media (which by many is supposed to be an 

 essentially different kind of action). Now, the objects of 

 nature, in the more strict sense of that phrase, are syntheta 

 of human perceptions and ultra-perceptions ; and syntheta of 

 perceptions cannot be what really act. Nevertheless, it is emi- 

 nently useful to carry on our investigation under the physical 

 hypothesis that it is they which act, and to confine our efforts 

 to tracing out what effects this action must be supposed 

 capable of producing, and under what laws it must operate, 

 in order that it may account for what occurs in nature. 

 This, however, is felt by many persons to be too abstract an 

 attitude of mind ; and to satisfy them, and create the plausi- 

 bility which they demand, by relieving the fundamental con- 

 ceptions of what is oppressively felt as the absurdity of 

 supposing that syntheta of perceptions act, it is usual to 

 supplement these syntheta by piling an aerial Pelion upon 

 this solid Ossa, and by supposing that in addition to the 

 sensible object which occupies any portion of space there is 

 what is called its material substance occupying the same 

 position, which, partly directly and partly by its motions, 

 acts on other material substances [the aether being one of 

 these material substances]. According to this, which is 

 the prevalent hypothesis among both scientific and non- 

 scientific men, it is these substances which travel about 

 through space ; and the sensible objects, which are what we 

 see and feel, are supposed to accompany them in their 

 wanderings by reason of the way in which they, the sub- 

 tances, act (usually through intermediate material agencies) 

 upon our organs of sense f. 



This is the usual point of view: but more careful thinkers 



* From the Scientific Proceedings of the Royal Dublin Society of the 

 26th of June, 1895. Communicated by the Author. 



f The author has endeavoured to trace out what it is that really occurs 

 in all such cases. See his paper "On the Relation between Natural 

 Science and Ontology," in the Scientific Proceedings of the Royal Dublin 

 Society, vol. vi. (1800) p. 475. 



