( 442 j 



Zdiilal intensity of llic tcri-csti-inl inaiz'nctisiii mul its sjtaco- aiul 

 tiiii('-\'ai"ialinii> mav hc dcIcniiiiKMl. ilii> iuciIkmI i> xcrv well adapted 

 ibr a laltoratory. w liicli has licoi Ituill wilhoiil ii-dii ami in a place, 

 wiiei'c no xihralioii-- or strav ciiitoiii^ in the cardi are to l>e feared. 



])i'ti'rniiii<itii>ii of fill' liorizmifdl nitciisitji i)f fin' frrri'strml 

 iiiiiijni'fisiii : II. 



'fo this purpose we lia\e followed the hililariiiauiietie iiielhod of 

 V. Koiii.RACscH * (Wied. Ann. 17. p 7.")7. IS.S2. The ahsolnic hitilar 

 magnelomeler Avas fas(ejie(l at the lop of a liiLili wdoden tripod. IM) 

 (Mil. to the noi-th and to the sonth of it the lan.ucjit ualvajionielers 

 were erected (ni pillars of freestone ccniciiiiMl on ilic hollom with plaster. 

 The dimensions of the niaüiictonielers of these uahanonieters are 

 altont the same as those of the ••Hlfeiil>einma<iiielometer'" of Kom,- 

 j{vrs( [i. hnt they diifer from it in an imp(trtant detail. The needle 

 with the niii-ror of the •'Klfenheinma.U'iietometer"' oscillates \\ ithiji a 

 small cylindric sjiace. whose sides are only a few inillimetei-s apart 

 and parallel to the plane of the mirror. \\\ this way the dam|)ii)g 

 lias heen obtained. 'Jhe local iidlnence of ilie insfi-nment is nearly 

 exclusively determinecl by the mauJielic or diamaunetic properties of 

 the material of ^^'hicll the front and lia(d< sides consist, which i.-- 

 nsnalh lilass. In conscMjnence of the small distance between the Jieedle 

 and the iilass walls this ijdlnence is \ariable with their relati\'e 

 |)o.sition. This i-enders the inaunetometer in this form nnsnitable for 

 ()bser\"ation> which i-eqnire a somewhat lonu'er lime, as we are Jiot 

 snre of a constant po-ition of the needle. It is theicfore that we 

 hax'e nnxlilied the inslrnment in such a way that ihe dislance of the 

 needle fi'om the fixed parts of the a])jiaratn> i> large enongh, the 

 damping being obtained in another manner. The space in which needle 

 and mii-ror oscillate is a \ertical. ihinw ailed tnrned cylinder of wood 

 with an intei-nal diameter of 4 cm. The frontwall has been |)ierced and 

 ronnd the hole a rim has been cementcMl in whi(di the glass front 

 Ills. A \ane of mica i> snspended on the cr()ss. which snp|)orts the 

 mirror and to \\ Inch ihe Jieedle i.^ ri\et(M|. Thi> w inu' can inoxc in 

 a narro\v space which is found in the ba>e of the in-lrumeiil and w li<»se 

 width amounts to a few m.in. In lhi< way a ^troni: air-damping 

 Iia> been obtained. 



In order to detei-nune \\\v local intluence the magnetometer wa^ 

 turned i-onnd the needle, sometimes in positive and sometimes in 

 negative direction: each time over an angle of 5". P>efore thcMnirror 

 a telescope Avith - a .scale wa> placed, and the distance had been 



