Intelligence and Miscellaneous Articles. 313 



ON THE HYPOTHESIS OF MOLECULAR VORTICES. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



As the article on Thermo-dynamics in the North British Review 

 is perhaps the most complete history of that science which has 

 yet appeared, and is written with a scientific precision which is 

 unusual in journals not specially devoted to science, I wish to cor- 

 rect an oversight that the reviewer has committed in describing the 

 "Hypothesis of Molecular Vortices," or "Centrifugal Theory of 

 Elasticity," as proposed by me in 1 849*. He speaks of atmospheres 

 of aether surrounding nuclei of ordinary matter; whereas in the 

 hypothesis as I put it forward, the nuclei perform the functions of 

 aether, and the atmospheres those of ordinary matter. Radiance is 

 supposed to consist in oscillations of the nuclei, transmitted in waves 

 by means of the forces which they exert on each other at a distance ; 

 and thermometric heat is supposed to consist in an agitation of the 

 atmospheres, producing outward pressure according to the known 

 laws of centrifugal force. Emission of radiance takes place when 

 the atmospheres whirl faster than the nuclei oscillate, so that the 

 nuclei are undergoing acceleration, and the atmospheres retardation ; 

 absorption of radiance takes place when the nuclei oscillate faster 

 than the atmospheres whirl, so that the nuclei are undergoing retar- 

 dation, and the atmospheres acceleration. In perfect gases, the 

 nuclei oscillate with little impediment from the atmospheres, and 

 the transmission of radiance is rapid ; in substances in a more dense 

 condition, each nucleus is, as it were, loaded with a part of its atmo- 

 sphere (like a pendulum in a resisting medium), and the transmis- 

 sion of radiance is slower. It is this peculiar view of the respective 

 functions of the nuclei and the atmospheres that constitutes the main 

 distinction between the hypothesis put forth by me, and other hypo- 

 theses involving atomic nuclei and atmospheres (as that of Mossotti), 

 or accounting for the phenomena of heat by molecular motions (as 

 that of Mr. Herapath). 



Of course a mechanical hypothesis does not form an indispensable 

 part of thermo-dynamics, more than of any other physical science ; 

 but if a hypothetical theory of thermo-dynamics is to be used, it 

 appears to me that its fundamental principles must be such as I have 

 described. 



I am, Gentlemen, 



Your most obedient Servant, 



Glasgow, March 1, 1864. W. J. Macquorn Rankine 



ON THE DEFLECTION OF THE MAGNETIC NEEDLE BY THE SECON- 

 DARY CURRENTS OF THE LEYDEN BATTERY. BY P. RIESS. 



The author obtained this deflection, which hitherto had not been 

 possible, by means of an apparatus which he had used before, and 

 to the construction of which an experiment of M. Gaugain had led. 

 * Transactions of the Royal Society of Edinburgh, 1850-51. 



