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hersey: laws of lubrication 



the resistance of the oil fihn. Four oils were used: sperm, lard, 

 ordinary mineral machine oil, and a heavy cylinder oil. The 

 chief source of uncertainty was in the determination of absolute 

 viscosities. The friction observations themselves were relatively 

 free from error. The machine was provided with an ordinary 

 complete bearing. The only feature which need be emphasized 

 is that the conditions of practice were thus more closely repro- 

 duced than could have been done on any machine with only a 

 half-bearing (as in the Tower type), or in which the two halves 

 of the bearing are both forced against the journal by external 

 pressure (as in the Thurston type). 



15. Summary of qualitative results. The following results 

 were obtained : 



Any change in viscosity produced the same effect whether the 

 viscosity was altered by changing oils or by changing tempera- 

 tures. There was no indication of complete "film rupture," 

 the film thickness decreasing continuously with increasing load 

 as far as the observations were carried. The above cited evi- 

 dence that film thickness increases with speed and viscosity 



