( 561 ) 



Colnnm I ~^,,, 1 <>* laWle X\ 11 uixcs Iho l(Mn|)eraliii'o coelTicicnts thus 



found tor llio (liifei'onl pressures ƒ/. 



Also a ('oi'reelioii was applied toi- tlu> diirereiicc in le\ el ol' tlie 

 iJiercnrv eolunins in the nianoineler and iIk^ experimental tnl»(\ lor 

 the expansion of the ^■olll)ne oï the manometer tnhe eansed hv the 

 inner pressure, and for the dilferenee in (•aj)illai\v depi-ession in the 

 two lubes. For the latter a se|)arate experiment has heen made to 

 determine the depression in a tnhe of the same inner I)oi'e as the 

 manometer tnhe. This eorreetion was 0.01 atmosphere. 



The manometer was read in the same wav as tiie piezometer 

 (see p. 558). The Icxel of the mereurv in the manometer Inlx» and 

 the tem[)eratnre of this \rere read before and after the reading- of 

 the menisens and the temperature of the experimental tube. The 

 temperature of the manometer eouhl be I'ead to within 0\05. 



x\fter the isothermal determinations the hydroüen manometer was 

 eonipai-ed with the standard manometers ('C()nun.N".50,Proe..bine 1899) 

 which ha\e beeJi verv aeciii-ately compared with the open man(M)iet<M- 

 by .^ciiALKWi.iK ((\)mm. N". 07, Proe. Dee. 1900 and Jan. 1901. 

 ('onim. N". 70, Pi-oe. ^lay and .bnie 1901). To render this possible 

 the liydrojj.en manometer had been constrneted so that the lowest 

 pressure wliieh could be read on it could still be measured with 

 the standard manometer IV'). Table XVIII f;i\es und<M' the headiii'; 

 A the pressure as measured with the hydrouen manomc^ter used by 

 me. under the headinf>: H the same pressure measured with the 

 standard manometer. 



TABLE XVIll. 



Obviously the agreement is quite satisfactory. This comparison 

 comes in the place of the determination of the normal volume after 

 the measurements, and also of more determinations of the normal 

 bore of the graduated stem. (Comp. p. 540j. As the there mentioned 

 mean |)ercenta,u-e dilferenee 0.19"',, is princi|)any due to the dilferenee 



9 For the way in wliicli this coinparison li.i.s l)cen inadc coinp. Verschaffelt, 

 Thesis for the doctorate p. 17. 



