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TRANSACTIONS OF THE SECTIONS. 



Section A— MATHEMATICAL AND rHYSK'AL SCIENCE 



Pi!i:sii)i:xT OP THE Section 

 I'lofcssor Sir WiM.lAM Thdaison, M.A., IJ-.U., D.C.I.., F.1!..SI,. .^ K,, K.ll.A.S. 



T! runs DA y, A uarsr i.'s. 



The rRi:.=>n)t:xT (Iclivert-d Iho following: Addivg.*: — 



Sfi'ps ti.icanh a Kiiuttc Tluori/ of Malli-r. 



The now woU-known kinetic theory of }?nse,s is n step .so iinportant iu the way of 

 explaining' .scicniin^rly .static properties nt" matter by motion, that it is scarcely 

 pos.-iiljle to help anticipating- in idea tlie aiiival at a cnniplcte theory of matter, in 

 wliich all its propertie.s will be seen to be nuirely attributes of motion. If 

 we are to look fir the origin of this idea, we must ^--.i back to Democritus 

 Epicurus and Lucretius. We may then, I believe, without mis.siuor a single 

 .'^tep, skip ],S()0 years. h;arly last century we lind in Malebranche's 

 ' Jteelierclio de la Aerite," the statement that 'J^aduieto des corps' depends on 

 'petits tourbilluas." ' These word.s, embedded in a hopeless mass of unintel- 

 li<,'ible statements of the phy.sieal, metapliysical, and theolog-ical philo.sophiea 

 of the day, and unsup])orted by an}' e.vjilanation, elucidation, or illustration 

 throuirhuut the re.st of the three volumes, and only marred by any other single 

 sentence or word to be found in the great book, still do expres.s a di.stinct concep- 

 tion, which forms a most remarkable step towards the kinetic theory of matter. 

 A little later we have Daniel ]3ernoulli's promulgation of what we now accept as 

 a surest article of scit^ntific faith — the kinetic theory of ga.ses. He, so far as 1 

 know, thought only of the IJoyle's and Harriot's law of the 'spring of air,' as 

 Boyle called it, without reference to change of temperature or the augmentation 

 (if its pressure if not allowed to expand for elevation of temperature, a phenomenon 

 which perhaps he scarcely knew, still less the elevation of temperature produced 

 by compression, and the lowering of temperature by dilatation, and the consequent 

 necessity of waiting for a fraction of a second or a few seconds of time (with 

 apparatus of ordinary experimental magnitude), to see a subsidence from a larger 

 change of pressure, down to the amount of change that verities Boyle's law. The 

 consideration of these phenomena forty years ago by Joule, in connection with 

 liernouUi'.s original conceptidu, I'ormed the foundation of the kinetic theory of 

 ga.ses as we now have it. But what a splendid and useful building has oeen 

 placed on this foundation by Clausius and Maxwell, and what a beautil'ul orna- 

 ment we see on the top of it in the radiometer of Orookes, securely attached to it 



' ' Treuve dc la supposition que j'ay faite : Que la matierc subtile ou 6th6ree est 

 ncccssairenicnt composeo do PETITS touiibillons ; et qu'ils sont les causes uatu- 

 relles de tous les changomcnts qui arrivent i\ la matiere ; ce que je contirme par 

 I'explication des elfets les plus gen6raux de la I'hysique, tels que sont la duret6 des 

 corps, leur tiuidite, Icur pesanteur, leur legercte, lalumierc "t la refraction ct r<!flcxion 

 de ses rayons.' — Jlalebranchc, llechen-hv dc la \ (ritr, 171-'. 



