THE MOLECULAR STRUCTURE OF MATTER.* 



By William Anderson. 



Five 3'ears ago, at Montreal, in bis atklress to the Mathematical Sec- 

 tion, Sir William Thomson took for his subject the ultimate constitu- 

 tion of matter, and discussed in a most suggestive manner the very 

 structure of the ultimate atoms or molecules. He passed in review the 

 theories extant on the subject, and poiiite<l out the progress which had 

 been made in recent years by the labors of Clausius, of Clerk Maxwell, 

 of Tait, and others, — among whom his own name (I may add) stands in 

 unrivalled prominence. I will not i)resume to enter the held of scien- 

 tific thought and speculation traversed by Sir William Thomson. I 

 I)ropose to draw attention oidy to some general considerations, and to 

 point out to what extent they practically interest tlie members of this 

 Section, 



In a lecture delivered at the Royal Institution last May, Professor 

 Mendeleeff attempted to show that there existed an analogy between 

 the constitution of the stellar universe and that of matter as we know 

 it on the surface of the earth, and that from the motions of the heav- 

 enly bodies down to minutest interatomic movements in chemical re- 

 actions, the third law of Newton held good, and that the application of 

 that law aftbrded a means of explaining those chemical substitutions 

 and isomerisms whicli are so characteristic, especially of organic chem- 

 istry. Examined from asufiicient distance, the planetary system would 

 appear as a concrete whole, endowed with invisible internal motions, 

 travelling to a distant goal. Taken in detail, each member of the 

 system may be involved in movements connected with its satellites, 

 and again each planet and satellite is instinct with motions which, 

 there is good reason to believe, extend to the ultimate atoms, and may 

 even exist, as Sir William Thomson has suggested, in the atoms them- 

 selves. The total result is complete equilibrium, and, in many cases, a 

 seeming absence of all motion, which is, in reality, the consequence of 

 dynamic equilibrium, and not the repose of immobility or inertness. 



The movements of the members of the stellar universe are many of 

 them visible to the naked eye, and their existence needs no demonstra- 

 tion ; but the extension of the generalization just mentioned to sub- 



* Presidential address before the Mechanical Science Section of the British Associ- 

 ation A. S., at Newcastle, September, 18b"J. {Ixcjjort of Britinh Association, vol. Lix, 

 pp. 718-732.) 



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