( 446 ) 



a few liines llie diifcM-ence aiiiormled (o oi' . Tlie mean 



(3000 4500 



of the hvo \ allies of // found in ilii> wnv. \vas laken as value of //. 



The hiiKjfiit iidlraiioiiK'tcrs. 



Fi\e diameters of llie laiiucnt ualxanonielcr -'iiorlir" \vere measured 

 l»v e(unparin,u- them willi a slainlard meter hv means of a kalheto- 

 meler ; tliev dilfei-ed less than 0.1 lu.m. Before the ohscrx'ations we 

 found for the mean Aaluc of the external diameter: 41.3833 cm. 

 /= 14" T), aftci' the observations we found 41.3842 e.ni., /=17°.5. 

 Reduction of tlie former \alne to the temjteratnre /=i7°.5 yields 

 41.3843 e.m. So the aureemcut is pci'leet. 



The rinu' of the taniienl uahanomeler "soutir' \a as not so |»er- 

 feetlv ('ii-cular: moi'eoxei- its sha|)e was not (|inte constant. Vet the 

 ditfeivnt determinations vielded mean values for the diameter which 

 a^ureed \erv well. Ten diametei's ha\e l»een measui-e<l. li\e on each 

 side, the distances of n\ Inch were as nearlv e(|ual as could he 

 ohtained. The \;dues found are: 



after the ol)sei'\ations 2 7/ = 40,445 cm. /= 17°. 3 



before the ol)sei-\ations 40,443cm. /=14".5 



a still earlier determination vielded 40,44() c.m. at /= 1!>°.8. WlieJi 



reduced to e(|ual leniperature these values dilfei' much less than 



1 

 40.000 ■ 



Foi' th<' (/('fi'j-ni//tti//(ni of ihi' Uih'iisilij of ihc ciirrciil sometimes 

 one, sometimes the other lan.uent uahanometer ^vas used. The curi-ent 

 was sui)[)lied \)\ a hatterv of 3 oi' 5 accumulatoi's : resistances of 

 about 20 ohms, two voltameters, a commntatoi' and one of the 

 galvanometers were insei'ted in the circuit. The intensitv of the 

 current varied bet\veen 0.30 and 0.45 amj)èi'es, the (|uantitv of 

 silver deposited was about 1 ,ui*am : the current })assed therefore during 

 48 or 32 minutes. Half a ndnute after the current was closed the 

 deflection of the tangent galvanometer was observed for the first 

 time, and turther e\ery nunute. While the current passed through 

 one of the galvanometei-s, the Nariations of the declination \\ ere 

 obserxed on the oiliei-. At ' , and at 'V , of the interxal during the 

 passage of the curi-e]it, the current was re\-ersed : during the short time 

 required for the rexersal, a short circuit \vas foj'med, so that the current 

 did not pass through the gal\ anometer: Hie error arising from this 

 circumstance is howcNer so small, that il cannot ha\(' any iiilliieuce 

 oji the result. The inllueiice of the re\ersal of the current in one 



