THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



DECEMBER 1885. 



L VII. On the Dilatancy of Media composed of Rigid Particles 

 in Contact, With Experimental Illustrations. By Professor 

 Osborne Reynolds, LL.D., F.R.S* 



[Plate X.] 



IDEAL rigid particles have been used in almost all attempts 

 to build fundamental dynamical hypotheses of matter : 

 these particles have generally been supposed smooth. 



Actual media composed of approximately rigid particles 

 exist in the shape of sand, shingle, grain, and piles of shot; all 

 which media are influenced by friction between the particles. 



The dynamical properties of media composed of ideal smooth 

 particles in a high state of agitation have formed the subject 

 of very long and successful investigations, resulting in the 

 dynamical theory of fluids. Also the limiting conditions of 

 equilibrium of such media as sand have been made the subject 

 of theoretical treatment by the aid of certain assumptions. 



These investigations, however, by no means constitute a 

 complete theory of granular masses ; nor does it appear that 

 any attempts have been made to investigate the dynamical 

 properties of a medium consisting of smooth hard particles, 

 held in contact by forces transmitted through the medium. 

 It has sometimes been assumed that such a medium would 

 possess the properties of a liquid, although in the molecular 

 hypothesis of liquids now accepted the particles are assumed 

 to be in a high state of motion, holding each other apart by 



* Comnmnicated by the Author. This Paper was read before Section A 

 of the British Association at the Aberdeen Meeting, September 10, 1885, 

 and again before Section B, at the request of the Section, September 15. 



Phil. Mag. S. 5. Vol. 20. No. 127. Dec. 1885. 2 L 



