Prof. J. Perry on Liquid Friction. 



451 



is as much consistency in all these results as might have been 

 expected. We lay most weight upon the results given in 

 Table III., which lead to the laws 



fi = 2*06 ((9-4-2) - 686 below 40° C; 

 /i = 21-67(0-4-2)- 1 ' 849 above 40° C. 



(9) 

 (10) 



We have searched in books in vain for a mention of a dis- 

 continuity in any other physical property of sperm-oil about 

 this temperature ; but we have already begun to experiment 

 on its other physical properties, as it is unlikely that there 

 should be a discontinuity in the law for the viscosity alone. 

 At the same time, we may say that our chemical friends see 

 no reason for a confirmation of our belief. 



In the tables we give the viscosity as calculated from these 

 formulae ; and it will be seen that they agree well enough 

 with the observed viscosities. 



Table IV.— March 18th, 1892. 

 (7= 6*15 centim. Temperature Constant, 17 0, 5 C.) 



n. 



D. 



y, or 

 D-K/+X). 



ix. 



36 



114 



~^16-41 



•351 



39 



121 



17-41 



•344 



54 



172 



24-75 



•352 



69 



245 



35-26 





80 



300 



4316 





92 



345 



49-64 





23 



74 



10-65 



•356 



16 



52 



7-48 



•360 



13 



41 



590 



•349 



8-75 



27 



3-98 



•349 





The column headed /n is 0*769 D/n(2 + \), and has no 

 meaning at a speed greater than the critical speed. The 

 critical speed, n c , is probably about 50. The first three and 

 last four values are probably measurements of fi. The average 

 value of these seven is /a=0*351. Formula (9) would make 

 /a to be 0-349. 



Plotting log?/ and logn as the coordinates of points on 

 squared paper, the points lie very nearly in a straight line 

 indicating yocn until the critical speed, about »i = 50, is 

 reached, and for all higher speeds the points lie nearly in 

 another straight line indicating y oc n l ' 2s . 



