796 HENRY S. WASHINGTON 
An analysis was made of a rather dark, fine-grained speci- 
men from Pigeon Hill quarry, whose sp. gr. was 2.69 at 17° C. 
It is notably less siliceous than the granite, contains more iron 
and lime and higher alkalis, though the ratio of soda to potash 
remains about the same. From its analogy with the analysis of 
rocks described below it may be called a quartz-syenite. Owing 
to the uncertainty of the composition of the hornblende and bio- 
tite no exact calculation of the mineralogical composition is 
possible. A rough estimate gives albite 36, orthoclase 33, quartz 
16, hornblende and biotite about 12, and magnetite, etc., 3 per 
cent. 
Akerite (augitic quartz-syenite) —The rocks belonging in this 
class were first noticed by Wadsworth’ in 1885 and were later 
described more in detail by Sears.?, Rosenbusch3 has expressed 
the opinion that these are related to the akerite type of syenites, 
a keen observation which my study of the rocks fully confirms. 
These rocks are found chiefly in the eastern part of Essex county, 
in Essex, Beverly, Manchester, Gloucester, and on Cape Ann. 
They lie between or around the granite areas, are connected 
with nepheline-syenites on the south, and have a general north- 
east-southwest trend. They appear to be almost as abundant as 
the granites. 
Although Sears speaks of the megascopic characters as being 
extremely variable yet ail the specimens collected by myself, 
as well as those given me by him, are fairly uniform. These 
show a granitic structure and are usually coarse-grained. The 
color even of the freshest specimens is greenish, which varies in 
shade from a dark greenish black to a light shade of greenish 
gray. They weather toa reddish color as Sears observed. The 
bulk of the rock is composed of feldspar which is of a deep 
greenish color, often fresh and with glistening cleavage surfaces, 
at other times dull and waxy. Quartz grains are present in vary- 
ing amount, some specimens showing considerable while others 
WADSWORTH, Geol. Mag., 1885, p. 207. 
2SEaARS, Buil. Essex Inst., Vol. XXIV, 1892, and Vol. XXV, 1893. 
3 ROSENBUSCH, Mikr. Phys., Vol. II, p. 127, 1896. 
