378 



Mr. J. L. Hogg on Friction in 



hydrogen over a range of pressures extending from atmo- 

 spheric pressure to 0*000016 mm. as indicated by the McLeod 

 gauge. 



Fourth, an equation relating pressure to decrement has 

 been obtained which applies well at all pressures below 

 0*1 mm. as far as pressures have been measured. The 

 equation, above mentioned, is of the form of Sutherland's 

 equation given tentatively in the former paper. It is 



h 



(4- 1 )-- 



In this equation k and c are constants to be determined from 

 the observations ; I is the decrement due to whatever friction 

 there is in the gas under examination, and to the friction in 

 the fibre ; p is pressure ; /j, is the decrement due to the 

 friction in the fibre. Its value has been measured directly. 

 The significance of the two slightly differing values of //,, 

 namely, p = 0*000020 and /* = 0-000022, which are found in 

 the following table, will appear later when the measurement 



Table I. — Hydrogen. 



Log. Dec. 



p (obseryed)i 



p (calculated) 

 •000020. 



p (calculated) 

 •000022. 



0-07942 

 0-07937 

 0-07927 

 007768 



760-0 

 435-0 

 103-0 

 8-89 







0-06902 

 0-05423 

 0-02861 

 0-01140 



1-24 

 0-410 

 0-105 

 0-0300 



0-109 

 00302 



0-109 

 00302 



0-01056 

 0-00936 

 0-00887 

 0-00710 



0-0275 

 0-0239 

 0-0225 

 00175 



0-0276 



0-0225 

 00174 



00275 



00225 

 0-0174 



0-00620 

 000525 

 0-00434 

 000426 



00150 

 00125 

 0-0102 



o-oioo 



00125 

 00102 

 0-00998 



0-0125 

 00102 

 0'00998 



0-00306 

 0-00220 

 000112 

 0-000459 



000704 

 0-00500 

 000250 

 000098 



0-00702 

 0-00497 

 0-00247 

 0-00097 



0-00702 

 0-00496 

 000246 

 0-00097 



0-000215 

 0-000029 



00042 

 0-000016 



0-00043 

 0-000020 



0-00043 

 0-000015 



