( 444 ) 



Jieedles inside tlic iiiauiKMoiiifHeis iiuiy Ix' deduced tVoiu di(^se data. 

 Tlic dislaiicc Ix'twceii llic siisjieiisiou-w ires aUoxc aiid l>el(i\\ , the 

 length of ihe ^\il•e^ and ihe weight which ihev sn[)]K»rt, are of 

 ])riniai-v inipoi'tancc^ for an accurate deterniinalion of the \ahie of 

 H y(^ }f for tlie hitihir niagnetonieler ( J/ =i niagnelii- moment of the 

 mau'net). Tiie Avires run ;dK)\e and l)eh»\\ closeh ah)im' two small 

 scales divided in ' ., m.ni. The distance Itelween the wire and Ihe 

 two adjacent di\isio]is of ihe scale is dclci'mincd hv a microscope 

 with ocular scale. 1 m.m. cori-esponds lo alxtui 23 dixisions of 

 the ocidar scale) and the distance l)<M\\'een the divisions of the two 

 scales is iletermincd with a c(Mn|iara1or. The distaiu-c i^ about 

 12.4 cm. These measurements lia\e becMi jterfoi-med before and 

 after the observations f August UKKS); the dilference of the distance 

 of the wires found in the two delcM-minalions amounted to: 

 above 0,004 m.m. below 0.002 m.m. 



The mean value of tlie two determinatioiis has been taken as Ihe 



distaiu'e during the obser\ali(Uis. It does \\n\ «blï'er nuu-e tVom those 



1 



values than -- . 



60000 



The length of the xvires has been delerunned before, after, and a 



few times l)etween the obserxations with the aid of a uiass scale. 



The extreme values of the lengths i-educed to the same temperatni-e 



diifered 0,13 m.m.: the length of the w ii'es l)eing al)on1 232 cm. 



1 

 An ei-roi' of O.J m.m. causes an erroi' in the result of -,——- . 



46000 



The jiieces, sn>|)('iidcd on the wii-esare: the horizontal crossd)ar with 

 its vei'tical rod and the beartM' of the magnet which are made of 

 aluminium, the magnet, and a \.ine of mica in diluted glycerin for 

 the damping. Tlies(> dillerenl j)ieces (with the exception of the mica- 

 vane) liaxe been weighed separately and together: the difference 

 was I mgr.. lli<^ total weight about IfiO gr. The weight of the 

 mica-xane with its >u>pension-w 're. imnierged in the li(piid >o fai' 

 as dni-ing the observations, was determined at : before the obser- 

 vations. 1.444 ur.. aftei'wai'ds 1,4^)7 ur.. average \alue 1,450 gr. 

 'I'he err(ti' w liicli may ensue from tlii'- dilference is not ureat : a 



dill"ei-(MU'e of i niür. uixes an eri'oi' of r— in the result. 



46000 



J/ 

 In order to deterinijie thexalneot j we mnst measure the polar 



distance of the magnet and the distance of the centers of the needles. 

 The polar distance of the magnet, 16,06 cm. long, was derived 



