336 MAdNKTlSM 



in the original direction \\as not changed in pha-c h\ ma 

 tion. The new component differed fro in it in pi -mail ai 



I)u Bois* measured tin- rotation on reflection at normal incidence 

 from mirrors worked on the cmN of iron, nickel, and cobalt 

 cores of electro-magnets. The cores were in tin- 

 spheroids. He Used this >hapc b. cording to the them 

 induction, if without the metal core the lie-Id is uniform, the 

 magnetisation I, when the metal is put in, is uniform 

 parallel to the axis. Measuring the rotation t and thcint 

 magnetisation I. du Hois found that e = KI, and he termed K the 

 Kerr constant. If the magnetisation was not normal to tin- 

 surface, then I was replaced bv I,., the normal component. K 

 found to be nearly independent of temp- and \\lnn t was 

 expressed in minutes it was found that K For iron IH> 

 for cobalt 0-0198, and for nickel -n-oHJO. while for magn. 

 it was +0*0 l!,'. Tin :.U r tor iron from 

 red to violet, while for Cobalt there \\as a minimum in tb 

 and for nickel a minimum in tin- \ello\\ of the .spectrum. 



The Zee man effect. 4 - Tin- ti. 



light which \\r ha\e a I read \ de- MisM in 



the light due to changes in ti \hieh it 



milled, oral \\hichit is reflected \\hentb -id. 



The modification^ ma\ be a-mlxd to a!' 



not to alterations in the Impicm 1 



alteration in \\a\e fre.pienc\ \\ In . lati\e n.. 



sourci- and medium and tin- condition i- st ia <l\. \ 



describi- an t-tfec-t of the magnetic condition on the light emitting 



elements of the source an alteration in the ! 



velocity, of the waves emitted. An alteration of this "kind. 



in vain by Faradax. perhaps obsemd b\ I as only cert- 



found by /c-eman in 1!)().| 



/ man placed a sodium Hame In'tween t: 



magnet which could create a powerful field through tin Mann-. 

 The light going out perpendicularly to tin- lines of fore. 

 ccpiatorially i\ed in a grating spectroscope, the 



having 1 U):JS hm-s to the inch and t 



dispersion. Hcfoiv the current circi:it uasclo>ed the Dlii. 

 fine and sharp. When the current \\as put on thev \\id- 

 perceptiblv. The red lithium lin 



similar effect. To show that the effect was directly du. 

 magnetic field and not to anv indin-i -tich as | 



ti-mperature through the change ot si, apt- of the ll . Mth 



gUlfl ends \\as put across the magnetic axis in place of the Hame. 

 A piece of sodium was ins^Tted in the tube, \\hich \v a -> heated so 

 that sodium vapour \\a> formed. A b-am of white light from an 



* /'//;/. May. xxix. --0). 



t '/ ' Mircht* in Magnfttt-Optict, Macmilla < t 191:1. 



* /'////. M,,,,. i:-|, xliii. p. . 



