

1890.] Slipping at the Boundary of a Liquid in Motion. 225 



from different thermometers vary considerably, intermediate tempera- 

 tures deduced from these curves are in practical agreement. 



II. That thermometers made and graduated as described may be 

 used for the accurate determination of temperatures up to about 

 500 C. 



II. " On the alleged Slipping at the Boundary of a Liquid in 

 Motion." By W. C. DAMPIER WHETHAM, B.A., Coutts 

 Trotter Student of Trinity College, Cambridge. Commu- 

 nicated by J. J. THOMSON, M.A., F.R.S., Cavendish Pro- 

 fessor of Experimental Physics, Cambridge. Received 

 June 7, 1890. 



(Abstract.) 



The experiments of Helmholtz and Piotrowski* on the oscillations 

 of a metal sphere suspended bifilarly, and filled with various liquids, 

 gave finite values to the slipping coefficients. The inside of the sphere 

 was gilded and polished, and the value obtained for the coefficient X 

 was, in the case of distilled water, 2'3534 mm. From some experi- 

 ments of Girardf on transpiration through copper tubes, Helmholtz 

 deduces the value X = O3984 mm. for water flowing past a copper 

 surface. 



In treatises on hydrodynamics, it is shown that when the motion 

 through a tube is linear, the flux is 



i \z - i iz 



* * ' 





In Helmholtz's notation this becomes (/> being taken as unity) 



^^Ov-^) 

 ft 



Putting r = 0-05 and X = 0-23534, we get 



j^Pi-aJ x 117-67x10-6; 

 fit 



whereas if there is no slip, so that X vanishes, the flux becomes 

 <PiZ^g) x 6-25X10-6. 



* ' Sitzungsberichte der Wiener Akademie,' vol. 40. 

 t ' Mernoires de 1'Institut,' 1813 1815. 



