( 385 ) 



tliat of the negative extinclioii ^villl referoiit'o to the (nice of y' (010) 

 on (he plane {JS^). 



Fis. 6. 



The (iii'iire is \\ i(h r('L>;ai(l (o tlie axes (}/^ and (JQ quite sym- 

 metrical again, in the same way as tig. 2 shows for the isogyres with 

 resj)ect (o the acnte bisectrix, because the i)oints here correspond 

 to the value : 



, , t — sur V .fi/i'^ (( 1 1 — .■<tn'^V cos^ a 



<P =^ h O'l cot I ; ; — . j . Sai iV I — 



sin 2« . sin^ V sin x sin 2« sm* V 



— h(t ft/ (.^lu ,1' t(j <t) r= y' — 8' . 



'1 — siii'^V sin'' (>. 1 1 — sin^Vcos'^a 



<p' = { b;/ cot ( — -^ ^-— -^-- . \ . ,in X 1 + 



sin Zu . snr V sin n; sin 2a sin' F ' 



-)- Ix/ f (J {sin ,r, cot a) =r ?/' — 8". 



26^ 



