THE STRATIFIED ROCKS OF ESSEX COUNTY. 45 
clase deeply kaolinized ; both the plagioclase and the or- 
thochise having numerous inclusions of quartz and biotite. 
There are also grains of epidote and fine dust-like ferrite, 
and niuscovite plates arranged parallel to the bedding. 
Microscopic structure of section of specimen (No. HI) 
from John Nojes' Copper Mine, Newbury, closely resem- 
bles the sections from Boxford (Nos. 109, 110) excepting 
that there is more biotite, that numerous cubes of iron 
pyrite are scattered through the dust-like ferrite and that 
microliths are of numerous occurrence. 
In the northern part of the county, occupying nearly the 
whole of the region known as Ballard Vale, West Ando- 
ver, South Lawrence, a part of North Andover, Bradford, 
Haverhill at Ayer Village, and passing into New Hamp- 
shire, is a coai'se granitoid gneiss cut by dykes of eruptive 
hornblendic granite and diorite. In Andover and North 
Andover the strike of this gneiss is east 40° north, paral- 
lel to the metamorphic slate, dij) 35° southwest. A large 
area of this jjneiss in West Andover and South Lawrence 
has been opened for quarrying purposes and fine exposures 
may be seen in a quarry at South Lawrence worked by Mr. 
Jesse Moulton. The strike at this point is east 20° north, 
dip 85° south of west. The microscopic structure of sec- 
tions of this rock is : coarse masses of orthoclase, micro- 
dine, quartz, muscovite, garnets cemented together by a 
thin film of secondary quartz. Numerous inclusions of 
quartz, biotite and muscovite are seen in the feldspars. 
I have traced this gneiss b}' means of numerous outcrops 
through South Hampton, Hampton and Rye to the Isles of 
Shoals. At E,ye an old quarry oflers good facilities for 
study, and specimens received from Appledore Island are 
of the same character and show the same microscopic 
structure in thin section. 
At Folly Point, Lanesville, and also at West Glouces- 
