802 HENRY S. WASHINGTON 
color and granitic structure. The feldspar is white; nepheline 
gray or brownish, with occasional yellow or gray cancrinite and 
blue sodalite which is abundant in certain veins on Salem Neck 
and elsewhere. Biotite, hornblende and aegirite are common, 
but are very irregularly distributed. Often they are scattered 
uniformly through the mass, but again they are rare or else 
abundant, and any one may predominate to the exclusion of the 
others. Occasional small brown crystals of zircon are seen, 
often of some size, but it never rises above the rank of an acces- 
sory, so that the name zircon-syenite, which has been applied to 
these rocks is quite unjustified. Magnetite is not uncommon, 
sometimes in large grains, and pyrrhotite is seen in one speci- 
men. 3 
In thin section the feldspars, chiefly albite and orthoclase, 
show less tendency to microperthitic intergrowth than in the 
granites, though such are not rare. The orthoclase is frequently 
in Carlsbad twins, and the albite shows twinning lamelle, but 
both are found in simple crystals. Microcline, spoken of by 
Rosenbusch as abundant, is rare in my sections. The nepheline 
calls for no special comment. While usually interstitial between 
the feldspars, small, stout prisms are often included in them. 
Sodalite is rare in the sections. In the rock from Mackerel 
Cove and from Great Haste Island it occurs decomposed to a 
dull, fine-grained aggregate (Sfreustein) interstitial between the 
feldspars. This decomposition has taken place while the nephe- 
line has remained perfectly fresh. Cancrinite, colorless in thin 
sections, was observed in the syenite from Salem Neck in small 
amount, but elsewhere was rare. It was identified by its cleav- 
age and high birefringence. 
Perhaps the most common of the ferromagnesian minerals is 
a deep brown, highly pleochroic biotite, which forms thick plates 
or stout prisms. An olive-green biotite also occurs on Salem 
Neck, but is much less common. MHornblende is not very abun- 
dant, except in the foyaites of Salem Neck. It is greenish-brown, 
or a deep olive-green, and highly pleochroic, and much resem- 
bles the aegirite. Ina few cases it occurs as a border around 
