[ADAMS 4 BARLOW] ALKALI SYENITES OF EASTERN ONTARIO 21 



amined between crossed niçois in convergent light, a black cross is seen, 

 thickened towards the intersection of the amis. This cross, on revolv- 

 ing the stage, divides into two hyperbolas, but these separate from one 

 another but very little and appear to separate less than they really do, 

 on account of the fact that the low double refraction and deep colour 

 of these sections cause the hyperbolas to be ill-defined, while the whole 

 lield is very dark. The dispersion, however, makes itself evident in the 

 varying colours on the sides of the hyperbolas. When, however, a gyp- 

 sum plate giving a red of the first order, is inserted above the objective, 

 the hyperbolas Ijecome a little better defined, although still not sufficiently 

 definite to allow the axial angle to be accurately measured. The axial 

 an,o;le is found to be over 30°, possibly as much as 45°, which, however, 

 is still very small for hornblende, being about one-half the usual value.^ 

 This hornblende resembles a variety intergrown with the augite in the 

 nepheline syenite from the Corporation Quarry at Montreal. It also 

 resembles in some respects the variety described by Haekman under the 

 name " arfvedsonite " occurring intergrown with asgirine in the nepheline 

 syenite from Uraptek in the Kola Peninsula.- The Kola hornblende 

 is much lighter in colour than that from either of the Canadian locali- 

 ties. 



This hornblende was analyzed by Dr. Harrington with the follow- 

 ing results : — 



SiO^ 34.184 



TiO^ 1.537 



AUO3 11.517 



Fe^^Og 13.631 



FeO 31.979 



MnO .639 



CaO 9.867 



MgO 1.353 



K.0 3.386 



Na^O 3.390 



H2Ô .348 



99.601 

 Specific gravity 3.433 



1 Am. Jour. Sc. Vol. XLVIII, 3rd Series, 1894, p. 13, and Am. Jour. Sc. Vol. 

 1. 4th Series, 1896, p. 210-218. 



■' Can. Rec. Se. Vol. VII. 1896-97, pp. 77-87. 



