﻿a Problem in Viscosity. 



1013 



If the theory given is correct, the points should lie on a 

 smooth curve. They do actually lie on such a curve within 

 experimental error, and the curve is seen to be very nearly 

 a straight line. All our measurements on wires can simply 

 be expressed by the formula 



(10) 



= 4-8 2! 



the constant 4*8 above being empirical. 



It appears, then, that the two extreme cases considered 

 theoretically, namely, all gravity and all surface-tension, are 

 easily realized. Indeed, we have not realized an intermediate 

 case, although it would probably be possible to obtain 



Fiff. 6. 

































- / 





1*8 































V 





1-6 





























/ 































/ 









1-4 

























A 































/ 













12 





















/ 



/° 



























o 



O 



/ 















y h> 

















o 



/> 































y 



o 

















0-8 















/ 































/ 



/ 





















0-6 













/ 































/o 



o 























0-4 









0' 































? 



' 



























0-2 





v 



' 































r 

































/ 

































0-1 



0-2 



YZL 



T 



0-3 



it with cylinders of greater radius. Further, it appears 

 that there is no special force of ' cohesion ' between solid and 

 liquid surfaces which can produce a film even as thick as 

 the thinnest we have examined (0 00007 cm.). If v were 

 infinitely small, i. e., if the surface were allowed to drain for 

 an infinite time, there is no evidence that the film would 

 not be completely removed, or at least reduced to molecular 

 thickness. The only action between solid and liquid im- 

 portant in these experiments is that which prevents slip at 

 the interface. It follows that the coating should be in- 

 dependent of the surface of the solid so long as the liquid 

 wets it at all. As far as our experience goes the conclusion 



