Dr. Pcrchal on Attra^lon and Repulfion, 445 



Facts and Queries relative to Attraction and 

 Repulsion. By Thomas Percival, M.D. ^c. 



To the Literary and Philosophical Society. 



Manchester, Dec. 5, 1784. 



I COMMUNICATED to you, a few weeks 

 ago, fome curious and valuable obfervations, 

 on the phenomena which take place between 

 oil and water, tranfmitted to me by my learned 

 and very ingenious friend Dr. Wall, of Oxford. 

 My engagements deprived me of the pleafure 

 and inftrudion, of attending their difcuffion in 

 the fociety: And, folicicous to recover what I 

 have left, I truft you will indulge me with per- 

 mifTion, to recall your attention to the Aibje<51:, 

 by the recital of a few mifcellaneous fads and 

 enquiries, which the .perufal of that paper fug- 

 gefted to my mind. 



I. If a glafs tumbler, containing equal parts 

 of water and of oil, in fuch quantity as to occupy 

 two thirds of it, be fufpended by a cord, and 

 fwung backwards and forwards, the oil will 

 remain perfedly fmooth and undifturbed, whilfl: 

 the water, below, is in violent commotion. But 

 if the oil be poured out, and its place fupplied 



with 



