José M. SoisRAi : <)n a Granite of Hemson (SwedenJ 125 



In a seciion nearly parallel lo (oío) I found the position of the 

 axes of the ellipsoid as follows : Np[N=i°i; II = 7°5 right] ;-Nm 

 [N = 2o8"3 ; H = i2°o right] ; and the position of (ooi) : [N = 82°3 ; 

 H=--3°44']; Ihai of (110) : [N = i3°5; H = 9"22']. One of the opti- 

 eal axes was 5/i°28' forward, the other axis 3q°9' backwards. 



Froni these data we have : — 2V=86°2o', <£[Ng Np (ooi)] = n°o, 

 <[Nm Np (ooi)] = 8a»8, <£[Ng Nm (oói)] =8a°5, <£.[(ooi) (iío)] 

 = 68°. Extinction in section J_Ng = 7°8. 



In a section nearly parallel to (ooi) it was very diííicult to íiiid 

 the positions of extinction as a consequence of the fineness of the 

 twinning lamellae. Furthermore the (oí o) cleavage was not good. 



Por this reason the observations are less exact than in the foréngoing case. 



For the lirst system of twinning lamellae the position of the axes 

 of the ellipsoid are : Np 1 [N = 1 1 1°5, II = 3°5 left], Ng 1 [N = io,9°5, 

 II = io°6 right]. For the the second system of twinning- lamellae I 

 found Np 2 [N = i46°5, II = o], Ng 2 [N = 2o5°6, H = 2O"0 right]. 

 For the brachypinacoidal cleavage (oio)[N = i29°i, H = 2°i left]. 

 .■.<£ [NmiNpi, Nm 2 Np 2 ] = 35°; <£[(oio), NpNm] = i7°6; <£j"(oio), 

 NgNm] = io7°4. 



The microcline of this rock appears altered to muscovite and kaoli- 

 nite. It is generally but little decomposed. 



Intergrowth of microcline and albite is common. It appears that 

 this albite has abont the same optical properties as the albite crys- 

 lallized independently. The diíferences observed are within the iimits 

 of error of observation, but perhaps it is somewhat less calcic. 



Albite. -- In a section near to the macropinacoid I found for 

 the (i) individual in albite twinning : Ng ] [N = 26i°2 ; H = 9°5 right], 

 Nmi[N=i65°3, H=25°8 left]. Axis 4o°i'8 backwards.-. +2 V=77°56'. 



For (oio)[N = 275°o, H = i°5 right] <£ [(01.0) Nm 1 Np^}= i6°o 

 <C[(oio)NgiNp 1 ] = 72°7, [(oio)Ng 1 Nmi] =-- 89°5. 



For the individual (2): Ng 2 [N = 28o°5, H = 2°o left]; Nm 2 

 [X^ 19203, H = 27°o right]. Axis ^fi' f \ forward. ■.-¡-2V = 77°55 / . 

 (oio)[N = 2G7°6, H = 6°o right]<£|"(oio)Nm 2 Np 2 ] = i5°o; <¿[(oio) 

 Ñg2Np 2 ] = 73"5, <£[(oio)Ng 2 Nm 2 ] = 89 o 1 . . 



In a section near the brachypinacoid (at 22 o from a plañe J_Ng), I 

 observed: Nm[N=i58°2, H = i6°5 left], Np[N=2 52°o, H = i4°5 

 left]. (001) cleavage : [N = i4i°o, II = 4°9 right]. The proximal op- 

 tic axis 2 3°37' forward, the distal optic axis 53°48'6 backwards 

 ..._i_ 2 V = 77 ° 2 6'; <£[NgNp, (ooi)] = 2 7 °o;<[N g Nm,(ooi)]=68°2 

 <jC[NpNm, (001)] = 75°o. 



