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Physics. — '' f.'<i>llii'riiiah of mu'liiri's nf o.niiji'n and ciirhaii (lio.ridi'. 

 I. rile <■<! Iihr<(ti())i at' iiKiiniiniicr (I ml nii'zoiiK'tcr /u fit's". \\\ 

 W. ][. Kkksom. ( oiiiiiiiiiiiculioii N" SS from the Pliysicjil 

 Lahui'atui'v at Loideii. Ity Piof. H. Kamkki.incjh Onnks. 



(Communicated in the nieetinfr (jf Se[)temhei "lij, 11>U3). 



§ 1. With a view to tlit* iii\ estijiatiuii^ of isotliennals. crilical 

 !\m\ condensation phenomena, of whieli I hct|»e to ^ive the i-e.siihs in 

 a foUowing- j)a|)er, I have earefiilly calihrated a inamtnieter and a 

 piezometer tube. The resnlts of these calibrations liave been i-e(biccd 

 acconbng lo a method lo which Pi'of. KAMEKi>iN(iH Onnks has drawn 

 my attention. Accofditiii lo that metliod the bore of tiie tnbe is repre- 

 sented by some terms of a series of FoiiuKK, tlie coeHicients of wliicli 

 are deri\ed from the observations. Thns we start from a continnons 

 representation of that bore iji opposition to the disconlinnons variations 

 wliich we miisl a(h»|>t when we (h'ri\e mean boi'es from the lengtli 

 of the mei'cnry cohimn at (Htlerenl j)hu'es, and regard lliem as bores 

 at the mi<hne of the cobimn. h'rom tiie foHo\ving may be judged 

 \vliat can be reached \)\ means of liiis metliod. ^i 



§ 2. Tlie majiometerlubi' was consti-iicted after tlie model (h'scribed 

 in ('omm, N" 50 of the IMiys. Pab. .il Leiden, 'differing lierein that 

 with a \ iew to the liigher pressnres a ring was bh)wn on to the 

 |)art A.', ihiis pi-e\enting the tnbe from mo\ing ahmjz; the cement 

 ill conse(pience of which the ihinwaUecl part '/, would be pi-essed 

 against tlie steel of the flanged lube, while the tnbe /r, is bent 

 parallel to the length of the tub" with the same purpose and in the 

 niannei' as has been desci-ibed in (.omm. N" ti9 (These Proc. Ill March 

 .')(). 11)01, p. ()25j. The stem (c., of fig. 4 ("omm. X" 50), graduate*! in mm., 

 had a leiiulh of' 50 cm., ihe iiuierbore was 0.81-5 mm., the oiitei' boi'e 

 6 mm., the capacity of the icsei'Noiiw/^ was about 25 ce., the widened 

 part (/j abo\ e had an inner bore of 2.<) mm., an outei" bore of 9 mm. and 

 had been lakeji so long that Ihe manometer, tilled \v\\U hydrogen, could 

 indicate j)ressures from about (50 to aboul 190 almosj)heres. The upper 

 cjlindrii'al j)arl of the experinieulal lube for the iinestigation of the 



^) In cousideiiition ol the circunislance tijut with tliese tubes observations have 

 been made which will form the subject of following papers, we shall give already 

 here for^the sake ot simplicity some data on stem calibration, together with some 

 remarks on the way in which the i'urlher data about these tubes are obtained. 



2) These Proc. 11 June '2i, iSOlt, |.. '2U. 



•^) See plate 1, fig. 4 of that Comm. 



